[llvm] 77b923d - [ConstantFolding] Do not remove side effect from constrained functions

[Serge Pavlov via llvm-commits]

Author: Serge Pavlov
Date: 2021-12-22T13:45:49+07:00
New Revision: 77b923d0dbe30f99b27ad533ef4322ee176b2046

URL: https://github.com/llvm/llvm-project/commit/77b923d0dbe30f99b27ad533ef4322ee176b2046
DIFF: https://github.com/llvm/llvm-project/commit/77b923d0dbe30f99b27ad533ef4322ee176b2046.diff

LOG: [ConstantFolding] Do not remove side effect from constrained functions

According to the discussion in https://reviews.llvm.org/D110322 the code
that removes side effect from replaced function call is deleted.

Differential Revision: https://reviews.llvm.org/D115870

Added: 
    

Modified: 
    llvm/lib/Analysis/ConstantFolding.cpp
    llvm/test/Transforms/InstSimplify/constfold-constrained.ll
    llvm/test/Transforms/InstSimplify/fdiv-strictfp.ll
    llvm/test/Transforms/InstSimplify/strictfp-fadd.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index e4920c351ccaf..922b38e927852 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1778,15 +1778,8 @@ static bool mayFoldConstrained(ConstrainedFPIntrinsic *CI,
 
   // If the operation does not change exception status flags, it is safe
   // to fold.
-  if (St == APFloat::opStatus::opOK) {
-    // When FP exceptions are not ignored, intrinsic call will not be
-    // eliminated, because it is considered as having side effect. But we
-    // know that its evaluation does not raise exceptions, so side effect
-    // is absent. To allow removing the call, mark it as not accessing memory.
-    if (EB && *EB != fp::ExceptionBehavior::ebIgnore)
-      CI->addFnAttr(Attribute::ReadNone);
+  if (St == APFloat::opStatus::opOK)
     return true;
-  }
 
   // If evaluation raised FP exception, the result can depend on rounding
   // mode. If the latter is unknown, folding is not possible.

diff  --git a/llvm/test/Transforms/InstSimplify/constfold-constrained.ll b/llvm/test/Transforms/InstSimplify/constfold-constrained.ll
index 4db5fbff30aff..2bfd4e03b1e6c 100644
--- a/llvm/test/Transforms/InstSimplify/constfold-constrained.ll
+++ b/llvm/test/Transforms/InstSimplify/constfold-constrained.ll
@@ -282,6 +282,7 @@ entry:
 define double @fadd_05() #0 {
 ; CHECK-LABEL: @fadd_05(
 ; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[RESULT:%.*]] = call double @llvm.experimental.constrained.fadd.f64(double 1.000000e+00, double 2.000000e+00, metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0]]
 ; CHECK-NEXT:    ret double 3.000000e+00
 ;
 entry:
@@ -293,6 +294,7 @@ entry:
 define double @fadd_06() #0 {
 ; CHECK-LABEL: @fadd_06(
 ; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[RESULT:%.*]] = call double @llvm.experimental.constrained.fadd.f64(double 1.000000e+00, double 2.000000e+00, metadata !"round.dynamic", metadata !"fpexcept.strict") #[[ATTR0]]
 ; CHECK-NEXT:    ret double 3.000000e+00
 ;
 entry:

diff  --git a/llvm/test/Transforms/InstSimplify/fdiv-strictfp.ll b/llvm/test/Transforms/InstSimplify/fdiv-strictfp.ll
index 82101a4ef8286..39222b1916afb 100644
--- a/llvm/test/Transforms/InstSimplify/fdiv-strictfp.ll
+++ b/llvm/test/Transforms/InstSimplify/fdiv-strictfp.ll
@@ -12,6 +12,7 @@ define float @fdiv_constant_fold() #0 {
 
 define float @fdiv_constant_fold_strict() #0 {
 ; CHECK-LABEL: @fdiv_constant_fold_strict(
+; CHECK-NEXT:    [[F:%.*]] = call float @llvm.experimental.constrained.fdiv.f32(float 3.000000e+00, float 2.000000e+00, metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0:[0-9]+]]
 ; CHECK-NEXT:    ret float 1.500000e+00
 ;
   %f = call float @llvm.experimental.constrained.fdiv.f32(float 3.0, float 2.0, metadata !"round.tonearest", metadata !"fpexcept.strict") #0
@@ -21,7 +22,7 @@ define float @fdiv_constant_fold_strict() #0 {
 
 define float @fdiv_constant_fold_strict2() #0 {
 ; CHECK-LABEL: @fdiv_constant_fold_strict2(
-; CHECK-NEXT:    [[F:%.*]] = call float @llvm.experimental.constrained.fdiv.f32(float 2.000000e+00, float 3.000000e+00, metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0:[0-9]+]]
+; CHECK-NEXT:    [[F:%.*]] = call float @llvm.experimental.constrained.fdiv.f32(float 2.000000e+00, float 3.000000e+00, metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0]]
 ; CHECK-NEXT:    ret float [[F]]
 ;
   %f = call float @llvm.experimental.constrained.fdiv.f32(float 2.0, float 3.0, metadata !"round.tonearest", metadata !"fpexcept.strict") #0
@@ -39,6 +40,7 @@ define float @frem_constant_fold() #0 {
 
 define float @frem_constant_fold_strict() #0 {
 ; CHECK-LABEL: @frem_constant_fold_strict(
+; CHECK-NEXT:    [[F:%.*]] = call float @llvm.experimental.constrained.frem.f32(float 3.000000e+00, float 2.000000e+00, metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0]]
 ; CHECK-NEXT:    ret float 1.000000e+00
 ;
   %f = call float @llvm.experimental.constrained.frem.f32(float 3.0, float 2.0, metadata !"round.tonearest", metadata !"fpexcept.strict") #0

diff  --git a/llvm/test/Transforms/InstSimplify/strictfp-fadd.ll b/llvm/test/Transforms/InstSimplify/strictfp-fadd.ll
index 61b2cafc63adf..61d06e964ac5c 100644
--- a/llvm/test/Transforms/InstSimplify/strictfp-fadd.ll
+++ b/llvm/test/Transforms/InstSimplify/strictfp-fadd.ll
@@ -363,6 +363,7 @@ define float @fold_fadd_qnan_qnan_ebmaytrap() #0 {
 
 define float @fold_fadd_qnan_qnan_ebstrict() #0 {
 ; CHECK-LABEL: @fold_fadd_qnan_qnan_ebstrict(
+; CHECK-NEXT:    [[ADD:%.*]] = call float @llvm.experimental.constrained.fadd.f32(float 0x7FF8000000000000, float 0x7FF8000000000000, metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0]]
 ; CHECK-NEXT:    ret float 0x7FF8000000000000
 ;
   %add = call float @llvm.experimental.constrained.fadd.f32(float 0x7ff8000000000000, float 0x7ff8000000000000, metadata !"round.tonearest", metadata !"fpexcept.strict") #0