[llvm] 7dd27a7 - InstSimplify: Fold fdiv nnan ninf x, 0 -> poison

[Matt Arsenault via llvm-commits]

Author: Matt Arsenault
Date: 2022-11-07T08:43:22-08:00
New Revision: 7dd27a75a261f57c6d038eb5faa421c49b12f1d5

URL: https://github.com/llvm/llvm-project/commit/7dd27a75a261f57c6d038eb5faa421c49b12f1d5
DIFF: https://github.com/llvm/llvm-project/commit/7dd27a75a261f57c6d038eb5faa421c49b12f1d5.diff

LOG: InstSimplify: Fold fdiv nnan ninf x, 0 -> poison

https://alive2.llvm.org/ce/z/JxX5in

Added: 
    

Modified: 
    llvm/lib/Analysis/InstructionSimplify.cpp
    llvm/test/Transforms/InstSimplify/fdiv.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 98db224e9e80..c8b796a34c6d 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -5461,6 +5461,10 @@ simplifyFDivInst(Value *Op0, Value *Op1, FastMathFlags FMF,
     if (match(Op0, m_FNegNSZ(m_Specific(Op1))) ||
         match(Op1, m_FNegNSZ(m_Specific(Op0))))
       return ConstantFP::get(Op0->getType(), -1.0);
+
+    // nnan ninf X / [-]0.0 -> poison
+    if (FMF.noInfs() && match(Op1, m_AnyZeroFP()))
+      return PoisonValue::get(Op1->getType());
   }
 
   return nullptr;

diff  --git a/llvm/test/Transforms/InstSimplify/fdiv.ll b/llvm/test/Transforms/InstSimplify/fdiv.ll
index 2b583a04818f..38e31257e185 100644
--- a/llvm/test/Transforms/InstSimplify/fdiv.ll
+++ b/llvm/test/Transforms/InstSimplify/fdiv.ll
@@ -64,8 +64,7 @@ define <2 x i1> @pr6096() {
 ; https://alive2.llvm.org/ce/z/JxX5in
 define float @fdiv_nnan_ninf_by_zero_f32(float %x) {
 ; CHECK-LABEL: @fdiv_nnan_ninf_by_zero_f32(
-; CHECK-NEXT:    [[FDIV:%.*]] = fdiv nnan ninf float [[X:%.*]], 0.000000e+00
-; CHECK-NEXT:    ret float [[FDIV]]
+; CHECK-NEXT:    ret float poison
 ;
   %fdiv = fdiv nnan ninf float %x, 0.0
   ret float %fdiv
@@ -73,8 +72,7 @@ define float @fdiv_nnan_ninf_by_zero_f32(float %x) {
 
 define float @fdiv_nnan_ninf_by_negzero_f32(float %x) {
 ; CHECK-LABEL: @fdiv_nnan_ninf_by_negzero_f32(
-; CHECK-NEXT:    [[FDIV:%.*]] = fdiv nnan ninf float [[X:%.*]], -0.000000e+00
-; CHECK-NEXT:    ret float [[FDIV]]
+; CHECK-NEXT:    ret float poison
 ;
   %fdiv = fdiv nnan ninf float %x, -0.0
   ret float %fdiv
@@ -98,8 +96,7 @@ define float @fdiv_nnan_ninf_by_poison_f32(float %x) {
 
 define <2 x float> @fdiv_nnan_ninf_by_zero_v2f32(<2 x float> %x) {
 ; CHECK-LABEL: @fdiv_nnan_ninf_by_zero_v2f32(
-; CHECK-NEXT:    [[FDIV:%.*]] = fdiv nnan ninf <2 x float> [[X:%.*]], zeroinitializer
-; CHECK-NEXT:    ret <2 x float> [[FDIV]]
+; CHECK-NEXT:    ret <2 x float> poison
 ;
   %fdiv = fdiv nnan ninf <2 x float> %x, zeroinitializer
   ret <2 x float> %fdiv
@@ -115,8 +112,7 @@ define <2 x float> @fdiv_nnan_ninf_by_undef_v2f32(<2 x float> %x) {
 
 define <2 x float> @fdiv_nnan_ninf_by_zero_undef_v2f32(<2 x float> %x) {
 ; CHECK-LABEL: @fdiv_nnan_ninf_by_zero_undef_v2f32(
-; CHECK-NEXT:    [[FDIV:%.*]] = fdiv nnan ninf <2 x float> [[X:%.*]], <float 0.000000e+00, float undef>
-; CHECK-NEXT:    ret <2 x float> [[FDIV]]
+; CHECK-NEXT:    ret <2 x float> poison
 ;
   %fdiv = fdiv nnan ninf <2 x float> %x, <float 0.0, float undef>
   ret <2 x float> %fdiv