[llvm] ada8a17 - [InstCombine] Fold abs intrinsic eq zero

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2020-09-05T15:11:38+02:00
New Revision: ada8a17d945c17c5603e24824f642ca199412adf

URL: https://github.com/llvm/llvm-project/commit/ada8a17d945c17c5603e24824f642ca199412adf
DIFF: https://github.com/llvm/llvm-project/commit/ada8a17d945c17c5603e24824f642ca199412adf.diff

LOG: [InstCombine] Fold abs intrinsic eq zero

Following the same transform for the select version of abs.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/test/Transforms/InstCombine/icmp.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 8860586c9aa1..350d00095c6f 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3088,6 +3088,13 @@ Instruction *InstCombinerImpl::foldICmpEqIntrinsicWithConstant(
   Type *Ty = II->getType();
   unsigned BitWidth = C.getBitWidth();
   switch (II->getIntrinsicID()) {
+  case Intrinsic::abs:
+    // abs(A) == 0  ->  A == 0
+    if (C.isNullValue())
+      return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
+                          Constant::getNullValue(Ty));
+    break;
+
   case Intrinsic::bswap:
     // bswap(A) == C  ->  A == bswap(C)
     return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),

diff  --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
index b284c5a2c840..a9bda13e15b9 100644
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/test/Transforms/InstCombine/icmp.ll
@@ -1094,8 +1094,7 @@ define zeroext i1 @cmpabs2(i64 %val) {
 
 define i1 @abs_intrin_eq_zero(i8 %x) {
 ; CHECK-LABEL: @abs_intrin_eq_zero(
-; CHECK-NEXT:    [[ABS:%.*]] = call i8 @llvm.abs.i8(i8 [[X:%.*]], i1 false)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[ABS]], 0
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[X:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %abs = call i8 @llvm.abs.i8(i8 %x, i1 false)
@@ -1105,8 +1104,7 @@ define i1 @abs_intrin_eq_zero(i8 %x) {
 
 define i1 @abs_intrin_ne_zero(i8 %x) {
 ; CHECK-LABEL: @abs_intrin_ne_zero(
-; CHECK-NEXT:    [[ABS:%.*]] = call i8 @llvm.abs.i8(i8 [[X:%.*]], i1 false)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i8 [[ABS]], 0
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i8 [[X:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %abs = call i8 @llvm.abs.i8(i8 %x, i1 false)