[DemandedBits] Add div/rem support

llvm/lib/Analysis/DemandedBits.cpp

@@ -246,6 +246,20 @@ void DemandedBits::determineLiveOperandBits(
     else
       AB &= ~(Known.One & ~Known2.One);
     break;
+  case Instruction::SRem: {
+    // urem and udiv will be converted to and/lshr
+    // multiple times and early on. So, we don't
+    // need to calculate demanded-bits for those.
+    const APInt *DivAmnt;
+    if (match(UserI->getOperand(1), m_APInt(DivAmnt))) {
+      if (DivAmnt->isPowerOf2()) {
+        unsigned Sh = DivAmnt->countr_zero();
+        AB = AOut & APInt::getLowBitsSet(BitWidth, Sh);
+        AB.setSignBit();
+      }
+    }
+    break;
+  }
   case Instruction::Xor:
   case Instruction::PHI:
     AB = AOut;

llvm/test/Analysis/DemandedBits/rem.ll

@@ -0,0 +1,83 @@
+; RUN: opt -S -disable-output -passes="print<demanded-bits>" < %s 2>&1 | FileCheck %s
+
+
+define i8 @test_srem_zext_trunc_const_amount2(i8 %a) {
+; CHECK-LABEL: 'test_srem_zext_trunc_const_amount2'
+; CHECK-DAG: DemandedBits: 0xff for   %rem = srem i32 %ext, 2
+; CHECK-DAG: DemandedBits: 0x80000001 for %ext in   %rem = srem i32 %ext, 2
+; CHECK-DAG: DemandedBits: 0x80000001 for 2 in   %rem = srem i32 %ext, 2
+; CHECK-DAG: DemandedBits: 0xff for %rem in   %rem.t = trunc i32 %rem to i8
+; CHECK-DAG: DemandedBits: 0xff for   %rem.t = trunc i32 %rem to i8
+; CHECK-DAG: DemandedBits: 0x80000001 for   %ext = sext i8 %a to i32
+; CHECK-DAG: DemandedBits: 0x81 for %a in   %ext = sext i8 %a to i32
+;
+  %ext = sext i8 %a to i32
+  %rem = srem i32 %ext, 2
+  %rem.t = trunc i32 %rem to i8
+  ret i8 %rem.t
+}
+
+define i8 @test_srem_const_amount_4(i32 %a) {
+; CHECK-LABEL: 'test_srem_const_amount_4'
+; CHECK-DAG: DemandedBits: 0xff for   %rem.t = trunc i32 %rem to i8
+; CHECK-DAG: DemandedBits: 0xff for %rem in   %rem.t = trunc i32 %rem to i8
+; CHECK-DAG: DemandedBits: 0xff for   %rem = srem i32 %a, 4
+; CHECK-DAG: DemandedBits: 0x80000003 for %a in   %rem = srem i32 %a, 4
+; CHECK-DAG: DemandedBits: 0x80000003 for 4 in   %rem = srem i32 %a, 4
+;
+  %rem = srem i32 %a, 4
+  %rem.t = trunc i32 %rem to i8
+  ret i8 %rem.t
+}
+
+define i8 @test_srem_const_amount_5(i32 %a) {
+; CHECK-LABEL: 'test_srem_const_amount_5'
+; CHECK-DAG: DemandedBits: 0xff for   %rem = srem i32 %a, 5
+; CHECK-DAG: DemandedBits: 0xffffffff for %a in   %rem = srem i32 %a, 5
+; CHECK-DAG: DemandedBits: 0xffffffff for 5 in   %rem = srem i32 %a, 5
+; CHECK-DAG: DemandedBits: 0xff for   %rem.t = trunc i32 %rem to i8
+; CHECK-DAG: DemandedBits: 0xff for %rem in   %rem.t = trunc i32 %rem to i8
+;
+  %rem = srem i32 %a, 5
+  %rem.t = trunc i32 %rem to i8
+  ret i8 %rem.t
+}
+
+define i8 @test_srem_const_amount_8(i32 %a) {
+; CHECK-LABEL: 'test_srem_const_amount_8'
+; CHECK-DAG: DemandedBits: 0xff for   %rem = srem i32 %a, 8
+; CHECK-DAG: DemandedBits: 0x80000007 for %a in   %rem = srem i32 %a, 8
+; CHECK-DAG: DemandedBits: 0x80000007 for 8 in   %rem = srem i32 %a, 8
+; CHECK-DAG: DemandedBits: 0xff for   %rem.t = trunc i32 %rem to i8
+; CHECK-DAG: DemandedBits: 0xff for %rem in   %rem.t = trunc i32 %rem to i8
+;
+  %rem = srem i32 %a, 8
+  %rem.t = trunc i32 %rem to i8
+  ret i8 %rem.t
+}
+
+define i8 @test_srem_const_amount_9(i32 %a) {
+; CHECK-LABEL: 'test_srem_const_amount_9'
+; CHECK-DAG: DemandedBits: 0xff for   %rem.t = trunc i32 %rem to i8
+; CHECK-DAG: DemandedBits: 0xff for %rem in   %rem.t = trunc i32 %rem to i8
+; CHECK-DAG: DemandedBits: 0xff for   %rem = srem i32 %a, 9
+; CHECK-DAG: DemandedBits: 0xffffffff for %a in   %rem = srem i32 %a, 9
+; CHECK-DAG: DemandedBits: 0xffffffff for 9 in   %rem = srem i32 %a, 9
+;
+  %rem = srem i32 %a, 9
+  %rem.t = trunc i32 %rem to i8
+  ret i8 %rem.t
+}
+
+define i8 @test_srem(i32 %a, i32 %b) {
+; CHECK-LABEL: 'test_srem'
+; CHECK-DAG: DemandedBits: 0xff for   %rem.t = trunc i32 %rem to i8
+; CHECK-DAG: DemandedBits: 0xff for %rem in   %rem.t = trunc i32 %rem to i8
+; CHECK-DAG: DemandedBits: 0xff for   %rem = srem i32 %a, %b
+; CHECK-DAG: DemandedBits: 0xffffffff for %a in   %rem = srem i32 %a, %b
+; CHECK-DAG: DemandedBits: 0xffffffff for %b in   %rem = srem i32 %a, %b
+;
+  %rem = srem i32 %a, %b
+  %rem.t = trunc i32 %rem to i8
+  ret i8 %rem.t
+}