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[Mips] Fix atomic min/max generate mips4 instructions when compiling for mips2 #149983

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[Mips] Fix atomic min/max generate mips4 instructions when compiling for mips2 #149983

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@yingopq yingopq commented Jul 22, 2025

Fix #145411.

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llvmbot commented Jul 22, 2025

@llvm/pr-subscribers-backend-mips

Author: None (yingopq)

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Fix #145411.

Patch is 31.58 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/149983.diff

2 Files Affected:

  • (modified) llvm/lib/Target/Mips/MipsExpandPseudo.cpp (+188-25)
  • (modified) llvm/test/CodeGen/Mips/atomic-min-max.ll (+521)
diff --git a/llvm/lib/Target/Mips/MipsExpandPseudo.cpp b/llvm/lib/Target/Mips/MipsExpandPseudo.cpp
index 199474fbd82d7..1c7ed37437aa7 100644
--- a/llvm/lib/Target/Mips/MipsExpandPseudo.cpp
+++ b/llvm/lib/Target/Mips/MipsExpandPseudo.cpp
@@ -433,13 +433,24 @@ bool MipsExpandPseudo::expandAtomicBinOpSubword(
   Register OldVal = I->getOperand(6).getReg();
   Register BinOpRes = I->getOperand(7).getReg();
   Register StoreVal = I->getOperand(8).getReg();
+  bool NoMovnInstr = (IsMin || IsMax) && !STI->hasMips4() && !STI->hasMips32();
 
   const BasicBlock *LLVM_BB = BB.getBasicBlock();
   MachineBasicBlock *loopMBB = MF->CreateMachineBasicBlock(LLVM_BB);
+  MachineBasicBlock *loop1MBB;
+  MachineBasicBlock *loop2MBB;
+  if (NoMovnInstr) {
+    loop1MBB = MF->CreateMachineBasicBlock(LLVM_BB);
+    loop2MBB = MF->CreateMachineBasicBlock(LLVM_BB);
+  }
   MachineBasicBlock *sinkMBB = MF->CreateMachineBasicBlock(LLVM_BB);
   MachineBasicBlock *exitMBB = MF->CreateMachineBasicBlock(LLVM_BB);
   MachineFunction::iterator It = ++BB.getIterator();
   MF->insert(It, loopMBB);
+  if (NoMovnInstr) {
+    MF->insert(It, loop1MBB);
+    MF->insert(It, loop2MBB);
+  }
   MF->insert(It, sinkMBB);
   MF->insert(It, exitMBB);
 
@@ -447,9 +458,19 @@ bool MipsExpandPseudo::expandAtomicBinOpSubword(
   exitMBB->transferSuccessorsAndUpdatePHIs(&BB);
 
   BB.addSuccessor(loopMBB, BranchProbability::getOne());
-  loopMBB->addSuccessor(sinkMBB);
-  loopMBB->addSuccessor(loopMBB);
+  if (NoMovnInstr) {
+    loopMBB->addSuccessor(loop1MBB);
+    loopMBB->addSuccessor(loop2MBB);
+  } else {
+    loopMBB->addSuccessor(sinkMBB);
+    loopMBB->addSuccessor(loopMBB);
+  }
   loopMBB->normalizeSuccProbs();
+  if (NoMovnInstr) {
+    loop1MBB->addSuccessor(loop2MBB);
+    loop2MBB->addSuccessor(loopMBB);
+    loop2MBB->addSuccessor(exitMBB, BranchProbability::getOne());
+  }
 
   BuildMI(loopMBB, DL, TII->get(LL), OldVal).addReg(Ptr).addImm(0);
   if (IsNand) {
@@ -526,7 +547,7 @@ bool MipsExpandPseudo::expandAtomicBinOpSubword(
       BuildMI(loopMBB, DL, TII->get(OR), BinOpRes)
           .addReg(BinOpRes)
           .addReg(Scratch4);
-    } else {
+    } else if (STI->hasMips4() || STI->hasMips32()) {
       // max: move BinOpRes, StoreVal
       //      movn BinOpRes, Incr, Scratch4, BinOpRes
       // min: move BinOpRes, StoreVal
@@ -538,12 +559,59 @@ bool MipsExpandPseudo::expandAtomicBinOpSubword(
           .addReg(Incr)
           .addReg(Scratch4)
           .addReg(BinOpRes);
+    } else {
+      // if min:
+      // loopMBB:  move BinOpRes, StoreVal
+      //           beq Scratch4, 0, loop1MBB
+      //           j loop2MBB
+      // loop1MBB: move BinOpRes, Incr
+      // loop2MBB: and BinOpRes, BinOpRes, Mask
+      //           and StoreVal, OlddVal, Mask2
+      //           or StoreVal, StoreVal, BinOpRes
+      //           StoreVal<tied1> = sc StoreVal, 0(Ptr)
+      //           beq StoreVal, zero, loopMBB
+      //
+      // if max:
+      // loopMBB:  move BinOpRes, Incr
+      //           beq Scratch4, 0, loop1MBB
+      //           j loop2MBB
+      // loop1MBB: move BinOpRes, StoreVal
+      // loop2MBB: and BinOpRes, BinOpRes, Mask
+      //           and StoreVal, OlddVal, Mask2
+      //           or StoreVal, StoreVal, BinOpRes
+      //           StoreVal<tied1> = sc StoreVal, 0(Ptr)
+      //           beq StoreVal, zero, loopMBB
+      if (IsMin) {
+        BuildMI(loopMBB, DL, TII->get(OR), BinOpRes)
+            .addReg(StoreVal)
+            .addReg(Mips::ZERO);
+        BuildMI(loop1MBB, DL, TII->get(OR), BinOpRes)
+            .addReg(Incr)
+            .addReg(Mips::ZERO);
+      } else {
+        BuildMI(loopMBB, DL, TII->get(OR), BinOpRes)
+            .addReg(Incr)
+            .addReg(Mips::ZERO);
+        BuildMI(loop1MBB, DL, TII->get(OR), BinOpRes)
+            .addReg(StoreVal)
+            .addReg(Mips::ZERO);
+      }
+      BuildMI(loopMBB, DL, TII->get(BEQ))
+          .addReg(Scratch4)
+          .addReg(Mips::ZERO)
+          .addMBB(loop1MBB);
+      BuildMI(loopMBB, DL, TII->get(Mips::J)).addMBB(loop2MBB);
     }
 
     //  and BinOpRes, BinOpRes, Mask
-    BuildMI(loopMBB, DL, TII->get(Mips::AND), BinOpRes)
-        .addReg(BinOpRes)
-        .addReg(Mask);
+    if (NoMovnInstr)
+      BuildMI(loop2MBB, DL, TII->get(Mips::AND), BinOpRes)
+          .addReg(BinOpRes)
+          .addReg(Mask);
+    else
+      BuildMI(loopMBB, DL, TII->get(Mips::AND), BinOpRes)
+          .addReg(BinOpRes)
+          .addReg(Mask);
 
   } else if (!IsSwap) {
     //  <binop> binopres, oldval, incr2
@@ -565,14 +633,37 @@ bool MipsExpandPseudo::expandAtomicBinOpSubword(
   // or StoreVal, StoreVal, BinOpRes
   // StoreVal<tied1> = sc StoreVal, 0(Ptr)
   // beq StoreVal, zero, loopMBB
-  BuildMI(loopMBB, DL, TII->get(Mips::AND), StoreVal)
-    .addReg(OldVal).addReg(Mask2);
-  BuildMI(loopMBB, DL, TII->get(Mips::OR), StoreVal)
-    .addReg(StoreVal).addReg(BinOpRes);
-  BuildMI(loopMBB, DL, TII->get(SC), StoreVal)
-    .addReg(StoreVal).addReg(Ptr).addImm(0);
-  BuildMI(loopMBB, DL, TII->get(BEQ))
-    .addReg(StoreVal).addReg(Mips::ZERO).addMBB(loopMBB);
+  if (NoMovnInstr) {
+    BuildMI(loop2MBB, DL, TII->get(Mips::AND), StoreVal)
+        .addReg(OldVal)
+        .addReg(Mask2);
+    BuildMI(loop2MBB, DL, TII->get(Mips::OR), StoreVal)
+        .addReg(StoreVal)
+        .addReg(BinOpRes);
+    BuildMI(loop2MBB, DL, TII->get(SC), StoreVal)
+        .addReg(StoreVal)
+        .addReg(Ptr)
+        .addImm(0);
+    BuildMI(loop2MBB, DL, TII->get(BEQ))
+        .addReg(StoreVal)
+        .addReg(Mips::ZERO)
+        .addMBB(loopMBB);
+  } else {
+    BuildMI(loopMBB, DL, TII->get(Mips::AND), StoreVal)
+        .addReg(OldVal)
+        .addReg(Mask2);
+    BuildMI(loopMBB, DL, TII->get(Mips::OR), StoreVal)
+        .addReg(StoreVal)
+        .addReg(BinOpRes);
+    BuildMI(loopMBB, DL, TII->get(SC), StoreVal)
+        .addReg(StoreVal)
+        .addReg(Ptr)
+        .addImm(0);
+    BuildMI(loopMBB, DL, TII->get(BEQ))
+        .addReg(StoreVal)
+        .addReg(Mips::ZERO)
+        .addMBB(loopMBB);
+  }
 
   //  sinkMBB:
   //    and     maskedoldval1,oldval,mask
@@ -601,6 +692,10 @@ bool MipsExpandPseudo::expandAtomicBinOpSubword(
 
   LivePhysRegs LiveRegs;
   computeAndAddLiveIns(LiveRegs, *loopMBB);
+  if (NoMovnInstr) {
+    computeAndAddLiveIns(LiveRegs, *loop1MBB);
+    computeAndAddLiveIns(LiveRegs, *loop2MBB);
+  }
   computeAndAddLiveIns(LiveRegs, *sinkMBB);
   computeAndAddLiveIns(LiveRegs, *exitMBB);
 
@@ -747,20 +842,41 @@ bool MipsExpandPseudo::expandAtomicBinOp(MachineBasicBlock &BB,
     llvm_unreachable("Unknown pseudo atomic!");
   }
 
+  bool NoMovnInstr = (IsMin || IsMax) && !STI->hasMips4() && !STI->hasMips32();
   const BasicBlock *LLVM_BB = BB.getBasicBlock();
   MachineBasicBlock *loopMBB = MF->CreateMachineBasicBlock(LLVM_BB);
+  MachineBasicBlock *loop1MBB;
+  MachineBasicBlock *loop2MBB;
+  if (NoMovnInstr) {
+    loop1MBB = MF->CreateMachineBasicBlock(LLVM_BB);
+    loop2MBB = MF->CreateMachineBasicBlock(LLVM_BB);
+  }
   MachineBasicBlock *exitMBB = MF->CreateMachineBasicBlock(LLVM_BB);
   MachineFunction::iterator It = ++BB.getIterator();
   MF->insert(It, loopMBB);
+  if (NoMovnInstr) {
+    MF->insert(It, loop1MBB);
+    MF->insert(It, loop2MBB);
+  }
   MF->insert(It, exitMBB);
 
   exitMBB->splice(exitMBB->begin(), &BB, std::next(I), BB.end());
   exitMBB->transferSuccessorsAndUpdatePHIs(&BB);
 
   BB.addSuccessor(loopMBB, BranchProbability::getOne());
-  loopMBB->addSuccessor(exitMBB);
-  loopMBB->addSuccessor(loopMBB);
+  if (NoMovnInstr) {
+    loopMBB->addSuccessor(loop1MBB);
+    loopMBB->addSuccessor(loop2MBB);
+  } else {
+    loopMBB->addSuccessor(exitMBB);
+    loopMBB->addSuccessor(loopMBB);
+  }
   loopMBB->normalizeSuccProbs();
+  if (NoMovnInstr) {
+    loop1MBB->addSuccessor(loop2MBB);
+    loop2MBB->addSuccessor(loopMBB);
+    loop2MBB->addSuccessor(exitMBB, BranchProbability::getOne());
+  }
 
   BuildMI(loopMBB, DL, TII->get(LL), OldVal).addReg(Ptr).addImm(0);
   assert((OldVal != Ptr) && "Clobbered the wrong ptr reg!");
@@ -803,7 +919,7 @@ bool MipsExpandPseudo::expandAtomicBinOp(MachineBasicBlock &BB,
       BuildMI(loopMBB, DL, TII->get(OR), Scratch)
           .addReg(Scratch)
           .addReg(Scratch2);
-    } else {
+    } else if (STI->hasMips4() || STI->hasMips32()) {
       // max: move Scratch, OldVal
       //      movn Scratch, Incr, Scratch2, Scratch
       // min: move Scratch, OldVal
@@ -815,6 +931,38 @@ bool MipsExpandPseudo::expandAtomicBinOp(MachineBasicBlock &BB,
           .addReg(Incr)
           .addReg(Scratch2)
           .addReg(Scratch);
+    } else {
+      // if min:
+      // loopMBB:  move Scratch, OldVal
+      //           beq Scratch2_32, 0, loop1MBB
+      //           j loop2MBB
+      // loop1MBB: move Scratch, Incr
+      // loop2MBB: sc $2, 0($4)
+      //           beqz	$2, $BB0_1
+      //           nop
+      //
+      // if max:
+      // loopMBB:  move Scratch, Incr
+      //           beq Scratch2_32, 0, loop1MBB
+      //           j loop2MBB
+      // loop1MBB: move Scratch, OldVal
+      // loop2MBB: sc $2, 0($4)
+      //           beqz	$2, $BB0_1
+      //           nop
+      if (IsMin) {
+        BuildMI(loopMBB, DL, TII->get(OR), Scratch).addReg(OldVal).addReg(ZERO);
+        BuildMI(loop1MBB, DL, TII->get(OR), Scratch).addReg(Incr).addReg(ZERO);
+      } else {
+        BuildMI(loopMBB, DL, TII->get(OR), Scratch).addReg(Incr).addReg(ZERO);
+        BuildMI(loop1MBB, DL, TII->get(OR), Scratch)
+            .addReg(OldVal)
+            .addReg(ZERO);
+      }
+      BuildMI(loopMBB, DL, TII->get(BEQ))
+          .addReg(Scratch2_32)
+          .addReg(ZERO)
+          .addMBB(loop1MBB);
+      BuildMI(loopMBB, DL, TII->get(Mips::J)).addMBB(loop2MBB);
     }
 
   } else if (Opcode) {
@@ -830,20 +978,35 @@ bool MipsExpandPseudo::expandAtomicBinOp(MachineBasicBlock &BB,
     BuildMI(loopMBB, DL, TII->get(OR), Scratch).addReg(Incr).addReg(ZERO);
   }
 
-  BuildMI(loopMBB, DL, TII->get(SC), Scratch)
-      .addReg(Scratch)
-      .addReg(Ptr)
-      .addImm(0);
-  BuildMI(loopMBB, DL, TII->get(BEQ))
-      .addReg(Scratch)
-      .addReg(ZERO)
-      .addMBB(loopMBB);
+  if (NoMovnInstr) {
+    BuildMI(loop2MBB, DL, TII->get(SC), Scratch)
+        .addReg(Scratch)
+        .addReg(Ptr)
+        .addImm(0);
+    BuildMI(loop2MBB, DL, TII->get(BEQ))
+        .addReg(Scratch)
+        .addReg(ZERO)
+        .addMBB(loopMBB);
+  } else {
+    BuildMI(loopMBB, DL, TII->get(SC), Scratch)
+        .addReg(Scratch)
+        .addReg(Ptr)
+        .addImm(0);
+    BuildMI(loopMBB, DL, TII->get(BEQ))
+        .addReg(Scratch)
+        .addReg(ZERO)
+        .addMBB(loopMBB);
+  }
 
   NMBBI = BB.end();
   I->eraseFromParent();
 
   LivePhysRegs LiveRegs;
   computeAndAddLiveIns(LiveRegs, *loopMBB);
+  if (!STI->hasMips4() && !STI->hasMips32()) {
+    computeAndAddLiveIns(LiveRegs, *loop1MBB);
+    computeAndAddLiveIns(LiveRegs, *loop2MBB);
+  }
   computeAndAddLiveIns(LiveRegs, *exitMBB);
 
   return true;
diff --git a/llvm/test/CodeGen/Mips/atomic-min-max.ll b/llvm/test/CodeGen/Mips/atomic-min-max.ll
index 85bf6d02c7d8f..050b3217fc577 100644
--- a/llvm/test/CodeGen/Mips/atomic-min-max.ll
+++ b/llvm/test/CodeGen/Mips/atomic-min-max.ll
@@ -3,6 +3,7 @@
 ; RUN: llc -mtriple=mips-elf -O0 -mcpu=mips32r6 -verify-machineinstrs %s -o - | FileCheck %s --check-prefix=MIPSR6
 ; RUN: llc -mtriple=mips-elf -O0 -mcpu=mips32r2 -mattr=+micromips -verify-machineinstrs %s -o - | FileCheck %s --check-prefix=MM
 ; RUN: llc -mtriple=mips-elf -O0 -mcpu=mips32r6 -mattr=+micromips -verify-machineinstrs %s -o - | FileCheck %s --check-prefix=MMR6
+; RUN: llc -mtriple=mipsel-elf -O0 -mcpu=mips2 %s -o - | FileCheck %s --check-prefix=MIPS2
 ; RUN: llc -mtriple=mipsel-elf -O0 -mcpu=mips32 -verify-machineinstrs %s -o - | FileCheck %s --check-prefix=MIPS32
 ; RUN: llc -mtriple=mipsel-elf -O0 -mcpu=mips32r2 -verify-machineinstrs %s -o - | FileCheck %s --check-prefix=MIPSEL
 ; RUN: llc -mtriple=mipsel-elf -O0 -mcpu=mips32r6 -verify-machineinstrs %s -o - | FileCheck %s --check-prefix=MIPSELR6
@@ -31,6 +32,33 @@ define i32 @test_max_32(ptr nocapture %ptr, i32 signext %val) {
 ; MIPS-NEXT:    jr $ra
 ; MIPS-NEXT:    nop
 ;
+; MIPS2-LABEL: test_max_32:
+; MIPS2:       # %bb.0: # %entry
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:  $BB0_1: # %entry
+; MIPS2-NEXT:    # =>This Inner Loop Header: Depth=1
+; MIPS2-NEXT:    ll $2, 0($4)
+; MIPS2-NEXT:    slt $3, $2, $5
+; MIPS2-NEXT:    move $1, $5
+; MIPS2-NEXT:    beqz $3, $BB0_3
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.2: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; MIPS2-NEXT:    j $BB0_4
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  $BB0_3: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; MIPS2-NEXT:    move $1, $2
+; MIPS2-NEXT:  $BB0_4: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; MIPS2-NEXT:    sc $1, 0($4)
+; MIPS2-NEXT:    beqz $1, $BB0_1
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.5: # %entry
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:    jr $ra
+; MIPS2-NEXT:    nop
+;
 ; MIPSR6-LABEL: test_max_32:
 ; MIPSR6:       # %bb.0: # %entry
 ; MIPSR6-NEXT:    sync
@@ -251,6 +279,33 @@ define i32 @test_min_32(ptr nocapture %ptr, i32 signext %val) {
 ; MIPS-NEXT:    jr $ra
 ; MIPS-NEXT:    nop
 ;
+; MIPS2-LABEL: test_min_32:
+; MIPS2:       # %bb.0: # %entry
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:  $BB1_1: # %entry
+; MIPS2-NEXT:    # =>This Inner Loop Header: Depth=1
+; MIPS2-NEXT:    ll $2, 0($4)
+; MIPS2-NEXT:    slt $3, $2, $5
+; MIPS2-NEXT:    move $1, $2
+; MIPS2-NEXT:    beqz $3, $BB1_3
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.2: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB1_1 Depth=1
+; MIPS2-NEXT:    j $BB1_4
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  $BB1_3: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB1_1 Depth=1
+; MIPS2-NEXT:    move $1, $5
+; MIPS2-NEXT:  $BB1_4: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB1_1 Depth=1
+; MIPS2-NEXT:    sc $1, 0($4)
+; MIPS2-NEXT:    beqz $1, $BB1_1
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.5: # %entry
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:    jr $ra
+; MIPS2-NEXT:    nop
+;
 ; MIPSR6-LABEL: test_min_32:
 ; MIPSR6:       # %bb.0: # %entry
 ; MIPSR6-NEXT:    sync
@@ -471,6 +526,33 @@ define i32 @test_umax_32(ptr nocapture %ptr, i32 signext %val) {
 ; MIPS-NEXT:    jr $ra
 ; MIPS-NEXT:    nop
 ;
+; MIPS2-LABEL: test_umax_32:
+; MIPS2:       # %bb.0: # %entry
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:  $BB2_1: # %entry
+; MIPS2-NEXT:    # =>This Inner Loop Header: Depth=1
+; MIPS2-NEXT:    ll $2, 0($4)
+; MIPS2-NEXT:    sltu $3, $2, $5
+; MIPS2-NEXT:    move $1, $5
+; MIPS2-NEXT:    beqz $3, $BB2_3
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.2: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB2_1 Depth=1
+; MIPS2-NEXT:    j $BB2_4
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  $BB2_3: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB2_1 Depth=1
+; MIPS2-NEXT:    move $1, $2
+; MIPS2-NEXT:  $BB2_4: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB2_1 Depth=1
+; MIPS2-NEXT:    sc $1, 0($4)
+; MIPS2-NEXT:    beqz $1, $BB2_1
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.5: # %entry
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:    jr $ra
+; MIPS2-NEXT:    nop
+;
 ; MIPSR6-LABEL: test_umax_32:
 ; MIPSR6:       # %bb.0: # %entry
 ; MIPSR6-NEXT:    sync
@@ -691,6 +773,33 @@ define i32 @test_umin_32(ptr nocapture %ptr, i32 signext %val) {
 ; MIPS-NEXT:    jr $ra
 ; MIPS-NEXT:    nop
 ;
+; MIPS2-LABEL: test_umin_32:
+; MIPS2:       # %bb.0: # %entry
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:  $BB3_1: # %entry
+; MIPS2-NEXT:    # =>This Inner Loop Header: Depth=1
+; MIPS2-NEXT:    ll $2, 0($4)
+; MIPS2-NEXT:    sltu $3, $2, $5
+; MIPS2-NEXT:    move $1, $2
+; MIPS2-NEXT:    beqz $3, $BB3_3
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.2: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB3_1 Depth=1
+; MIPS2-NEXT:    j $BB3_4
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  $BB3_3: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB3_1 Depth=1
+; MIPS2-NEXT:    move $1, $5
+; MIPS2-NEXT:  $BB3_4: # %entry
+; MIPS2-NEXT:    # in Loop: Header=BB3_1 Depth=1
+; MIPS2-NEXT:    sc $1, 0($4)
+; MIPS2-NEXT:    beqz $1, $BB3_1
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.5: # %entry
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:    jr $ra
+; MIPS2-NEXT:    nop
+;
 ; MIPSR6-LABEL: test_umin_32:
 ; MIPSR6:       # %bb.0: # %entry
 ; MIPSR6-NEXT:    sync
@@ -936,6 +1045,58 @@ define i16 @test_max_16(ptr nocapture %ptr, i16 signext %val) {
 ; MIPS-NEXT:    jr $ra
 ; MIPS-NEXT:    nop
 ;
+; MIPS2-LABEL: test_max_16:
+; MIPS2:       # %bb.0: # %entry
+; MIPS2-NEXT:    addiu $sp, $sp, -8
+; MIPS2-NEXT:    .cfi_def_cfa_offset 8
+; MIPS2-NEXT:    # kill: def $at killed $a1
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:    addiu $1, $zero, -4
+; MIPS2-NEXT:    and $6, $4, $1
+; MIPS2-NEXT:    andi $1, $4, 3
+; MIPS2-NEXT:    sll $10, $1, 3
+; MIPS2-NEXT:    ori $1, $zero, 65535
+; MIPS2-NEXT:    sllv $8, $1, $10
+; MIPS2-NEXT:    nor $9, $zero, $8
+; MIPS2-NEXT:    sllv $7, $5, $10
+; MIPS2-NEXT:  $BB4_1: # %entry
+; MIPS2-NEXT:    # =>This Inner Loop Header: Depth=1
+; MIPS2-NEXT:    ll $2, 0($6)
+; MIPS2-NEXT:    srav $4, $2, $10
+; MIPS2-NEXT:    sll $4, $4, 16
+; MIPS2-NEXT:    sra $4, $4, 16
+; MIPS2-NEXT:    or $1, $zero, $4
+; MIPS2-NEXT:    sllv $4, $4, $10
+; MIPS2-NEXT:    slt $5, $4, $7
+; MIPS2-NEXT:    move $3, $7
+; MIPS2-NEXT:    beqz $5, $BB4_3
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.2: # %entry
+; MIPS2-NEXT:    #   in Loop: Header=BB4_1 Depth=1
+; MIPS2-NEXT:    j $BB4_4
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  $BB4_3: # %entry
+; MIPS2-NEXT:    #   in Loop: Header=BB4_1 Depth=1
+; MIPS2-NEXT:    move $3, $4
+; MIPS2-NEXT:  $BB4_4: # %entry
+; MIPS2-NEXT:    #   in Loop: Header=BB4_1 Depth=1
+; MIPS2-NEXT:    and $3, $3, $8
+; MIPS2-NEXT:    and $4, $2, $9
+; MIPS2-NEXT:    or $4, $4, $3
+; MIPS2-NEXT:    sc $4, 0($6)
+; MIPS2-NEXT:    beqz $4, $BB4_1
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.5: # %entry
+; MIPS2-NEXT:    .insn
+; MIPS2-NEXT:  $BB4_6: # %entry
+; MIPS2-NEXT:    sw $1, 4($sp) # 4-byte Folded Spill
+; MIPS2-NEXT:  # %bb.7: # %entry
+; MIPS2-NEXT:    lw $2, 4($sp) # 4-byte Folded Reload
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:    addiu $sp, $sp, 8
+; MIPS2-NEXT:    jr $ra
+; MIPS2-NEXT:    nop
+;
 ; MIPSR6-LABEL: test_max_16:
 ; MIPSR6:       # %bb.0: # %entry
 ; MIPSR6-NEXT:    addiu $sp, $sp, -8
@@ -1476,6 +1637,58 @@ define i16 @test_min_16(ptr nocapture %ptr, i16 signext %val) {
 ; MIPS-NEXT:    jr $ra
 ; MIPS-NEXT:    nop
 ;
+; MIPS2-LABEL: test_min_16:
+; MIPS2:       # %bb.0: # %entry
+; MIPS2-NEXT:    addiu $sp, $sp, -8
+; MIPS2-NEXT:    .cfi_def_cfa_offset 8
+; MIPS2-NEXT:    # kill: def $at killed $a1
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:    addiu $1, $zero, -4
+; MIPS2-NEXT:    and $6, $4, $1
+; MIPS2-NEXT:    andi $1, $4, 3
+; MIPS2-NEXT:    sll $10, $1, 3
+; MIPS2-NEXT:    ori $1, $zero, 65535
+; MIPS2-NEXT:    sllv $8, $1, $10
+; MIPS2-NEXT:    nor $9, $zero, $8
+; MIPS2-NEXT:    sllv $7, $5, $10
+; MIPS2-NEXT:  $BB5_1: # %entry
+; MIPS2-NEXT:    # =>This Inner Loop Header: Depth=1
+; MIPS2-NEXT:    ll $2, 0($6)
+; MIPS2-NEXT:    srav $4, $2, $10
+; MIPS2-NEXT:    sll $4, $4, 16
+; MIPS2-NEXT:    sra $4, $4, 16
+; MIPS2-NEXT:    or $1, $zero, $4
+; MIPS2-NEXT:    sllv $4, $4, $10
+; MIPS2-NEXT:    slt $5, $4, $7
+; MIPS2-NEXT:    move $3, $4
+; MIPS2-NEXT:    beqz $5, $BB5_3
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.2: # %entry
+; MIPS2-NEXT:    #   in Loop: Header=BB5_1 Depth=1
+; MIPS2-NEXT:    j $BB5_4
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  $BB5_3: # %entry
+; MIPS2-NEXT:    #   in Loop: Header=BB5_1 Depth=1
+; MIPS2-NEXT:    move $3, $7
+; MIPS2-NEXT:  $BB5_4: # %entry
+; MIPS2-NEXT:    #   in Loop: Header=BB5_1 Depth=1
+; MIPS2-NEXT:    and $3, $3, $8
+; MIPS2-NEXT:    and $4, $2, $9
+; MIPS2-NEXT:    or $4, $4, $3
+; MIPS2-NEXT:    sc $4, 0($6)
+; MIPS2-NEXT:    beqz $4, $BB5_1
+; MIPS2-NEXT:    nop
+; MIPS2-NEXT:  # %bb.5: # %entry
+; MIPS2-NEXT:    .insn
+; MIPS2-NEXT:  $BB5_6: # %entry
+; MIPS2-NEXT:    sw $1, 4($sp) # 4-byte Folded Spill
+; MIPS2-NEXT:  # %bb.7: # %entry
+; MIPS2-NEXT:    lw $2, 4($sp) # 4-byte Folded Reload
+; MIPS2-NEXT:    sync
+; MIPS2-NEXT:    addiu $sp, $sp, 8
+; MIPS2-NEXT:    jr $ra
+; MIPS2-NEXT:    nop
+;
 ; MIPSR6-LABEL: test_min_16:
 ; MIPSR6:       # %bb.0: # %entry
 ; MIPSR6-NEXT:    addiu $sp, $sp, -8
@@ -2015,6 +2228,57 @@ de...
[truncated]

@Sirius902
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I built this PR from source on macOS and tried compiling the same program shown in #145411 but it seems the compiler ended up crashing.

❯ clang -c --target=mips-linux-gnu -mips2 -Oz -o main.o main.c
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: clang -c --target=mips-linux-gnu -mips2 -Oz -o main.o main.c
1.      <eof> parser at end of file
2.      Code generation
3.      Running pass 'Function Pass Manager' on module 'main.c'.
4.      Running pass 'Mips Branch Expansion Pass' on function '@min'
#0 0x00000001056704b8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/Users/chris/Dev/c/llvm-project/build/bin/clang-21+0x1026f44b8)
#1 0x000000010566e408 llvm::sys::RunSignalHandlers() (/Users/chris/Dev/c/llvm-project/build/bin/clang-21+0x1026f2408)
#2 0x000000010566f9b8 llvm::sys::CleanupOnSignal(unsigned long) (/Users/chris/Dev/c/llvm-project/build/bin/clang-21+0x1026f39b8)
#3 0x00000001055b6de8 CrashRecoverySignalHandler(int) (/Users/chris/Dev/c/llvm-project/build/bin/clang-21+0x10263ade8)
#4 0x000000019d114624 (/usr/lib/system/libsystem_platform.dylib+0x1804ac624)
#5 0x0000000103b4dec4 (anonymous namespace)::MipsBranchExpansion::handlePossibleLongBranch() (/Users/chris/Dev/c/llvm-project/build/bin/clang-21+0x100bd1ec4)
#6 0x0000000103b4dec4 (anonymous namespace)::MipsBranchExpansion::handlePossibleLongBranch() (/Users/chris/Dev/c/llvm-project/build/bin/clang-21+0x100bd1ec4)
clang: error: clang frontend command failed with exit code 139 (use -v to see invocation)
clang version 21.0.0git ([email protected]:yingopq/llvm-project.git 74af81c71078cdaf647d4435ee4c448edd88e8b8)
Target: mips-unknown-linux-gnu
Thread model: posix
InstalledDir: /Users/chris/Dev/c/llvm-project/build/bin
clang: note: diagnostic msg:
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang: note: diagnostic msg: /var/folders/tr/9sy58s854pj87w4pzstgbjcw0000gn/T/main-4881f1.c
clang: note: diagnostic msg: /var/folders/tr/9sy58s854pj87w4pzstgbjcw0000gn/T/main-4881f1.sh
clang: note: diagnostic msg: Crash backtrace is located in
clang: note: diagnostic msg: /Users/chris/Library/Logs/DiagnosticReports/clang-21_<YYYY-MM-DD-HHMMSS>_<hostname>.crash
clang: note: diagnostic msg: (choose the .crash file that corresponds to your crash)
clang: note: diagnostic msg:

********************

@yingopq
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yingopq commented Jul 31, 2025

Thanks, I would see this error.
I tested this issue using sudo ./build/bin/clang --target=mipsel-unknown-linux-gnu -march=mips2 -emit-llvm -S 1.c and sudo ./build/bin/clang --target=mipsel-unknown-linux-gnu -fuse-ld=/usr/bin/mipsel-linux-gnu-ld 1.ll -o a1main, so I did not find this error.

@yingopq yingopq force-pushed the Fix_bug_issue_145411 branch from 74af81c to cea3ce0 Compare August 1, 2025 07:21
@yingopq
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yingopq commented Aug 1, 2025

Hi @Sirius902,
I have fixed this error, could you help test again, thanks!

@yingopq yingopq force-pushed the Fix_bug_issue_145411 branch from cea3ce0 to 1e6567f Compare August 1, 2025 08:33
@Sirius902
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Hi @Sirius902, I have fixed this error, could you help test again, thanks!

Looks good to me, thanks! :)

❯ objdump -d main.o

main.o: file format elf32-mips

Disassembly of section .text:

00000000 <min>:
       0: 00 00 00 0f   sync <min>
       4: c0 82 00 00   ll      $2, 0x0($4)
       8: 00 45 18 2a   slt     $3, $2, $5
       c: 10 60 00 03   beqz    $3, 0x1c <min+0x1c>
      10: 00 40 08 25   move    $1, $2
      14: 10 00 00 02   b       0x20 <min+0x20>
      18: 00 00 00 00   nop <min>
      1c: 00 a0 08 25   move    $1, $5
      20: e0 81 00 00   sc      $1, 0x0($4)
      24: 10 20 ff f7   beqz    $1, 0x4 <min+0x4>
      28: 00 00 00 00   nop <min>
      2c: 00 00 00 0f   sync <min>
      30: 03 e0 00 08   jr      $ra
      34: 00 00 00 00   nop <min>

00000038 <max>:
      38: 00 00 00 0f   sync <min>
      3c: c0 82 00 00   ll      $2, 0x0($4)
      40: 00 45 18 2a   slt     $3, $2, $5
      44: 10 60 00 03   beqz    $3, 0x54 <max+0x1c>
      48: 00 a0 08 25   move    $1, $5
      4c: 10 00 00 02   b       0x58 <max+0x20>
      50: 00 00 00 00   nop <min>
      54: 00 40 08 25   move    $1, $2
      58: e0 81 00 00   sc      $1, 0x0($4)
      5c: 10 20 ff f7   beqz    $1, 0x3c <max+0x4>
      60: 00 00 00 00   nop <min>
      64: 00 00 00 0f   sync <min>
      68: 03 e0 00 08   jr      $ra
      6c: 00 00 00 00   nop <min>

@brad0
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brad0 commented Aug 1, 2025

cc @wzssyqa @topperc @MaskRay

@brad0
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brad0 commented Aug 17, 2025

cc @arsenm @topperc

arsenm
arsenm reviewed Aug 17, 2025
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Is there a reason mips is reinventing all this stuff in a machine pass? AtomicExpand should already handle all of this?

@yingopq
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yingopq commented Aug 19, 2025

Is there a reason mips is reinventing all this stuff in a machine pass? AtomicExpand should already handle all of this?

Sorry, I did not find this reason.

@yingopq
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yingopq commented Aug 21, 2025

Is there a reason mips is reinventing all this stuff in a machine pass? AtomicExpand should already handle all of this?

@nikic Did you the reason? Thanks.

@nikic
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nikic commented Aug 21, 2025

I think this is related to the problems in #25900 / #31368, where it's invalid to introduce additional intermediate stores from spilling.

@jrtc27
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jrtc27 commented Aug 21, 2025

Yeah AtomicExpand is fundamentally broken for LL/SC expansion unless your architecture places no limits on the number and type of instructions that can appear between the LL and SC.

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[clang] mips4 instructions generated when compiling for mips2
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@yingopq @llvmbot @Sirius902 @brad0 @nikic @jrtc27 @arsenm