[llvm] d686ea3 - [ConstantFolding] Guard against unfolded FP binop

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2022-07-08T17:45:33+02:00
New Revision: d686ea32b1af5f0a00fe577f530817c4214e16d0

URL: https://github.com/llvm/llvm-project/commit/d686ea32b1af5f0a00fe577f530817c4214e16d0
DIFF: https://github.com/llvm/llvm-project/commit/d686ea32b1af5f0a00fe577f530817c4214e16d0.diff

LOG: [ConstantFolding] Guard against unfolded FP binop

Check that the operation actually folded before trying to flush
denormals. A minor variation of the pr33453 test exposed this
with the FP binops marked as undesirable.

Added: 
    

Modified: 
    llvm/lib/Analysis/ConstantFolding.cpp
    llvm/test/Transforms/InstCombine/pr33453.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 85d9385236dca..aa4da27be4e57 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1397,6 +1397,8 @@ Constant *llvm::ConstantFoldFPInstOperands(unsigned Opcode, Constant *LHS,
 
     // Calculate constant result.
     Constant *C = ConstantFoldBinaryOpOperands(Opcode, Op0, Op1, DL);
+    if (!C)
+      return nullptr;
 
     // Flush denormal output if needed.
     return FlushFPConstant(C, I, /* IsOutput */ true);

diff  --git a/llvm/test/Transforms/InstCombine/pr33453.ll b/llvm/test/Transforms/InstCombine/pr33453.ll
index 5d496e76186aa..055ae274257c8 100644
--- a/llvm/test/Transforms/InstCombine/pr33453.ll
+++ b/llvm/test/Transforms/InstCombine/pr33453.ll
@@ -6,9 +6,11 @@
 
 define float @patatino() {
 ; CHECK-LABEL: @patatino(
-; CHECK-NEXT:    ret float fmul (float uitofp (i1 icmp eq (i16* getelementptr inbounds (i16, i16* @g2, i64 1), i16* @g1) to float), float uitofp (i1 icmp eq (i16* getelementptr inbounds (i16, i16* @g2, i64 1), i16* @g1) to float))
+; CHECK-NEXT:    [[FMUL:%.*]] = fmul float uitofp (i1 icmp eq (i16* getelementptr inbounds (i16, i16* @g2, i64 1), i16* @g1) to float), uitofp (i1 icmp eq (i16* getelementptr inbounds (i16, i16* @g2, i64 1), i16* @g1) to float)
+; CHECK-NEXT:    ret float [[FMUL]]
 ;
-  %call = call float @fabsf(float fmul (float uitofp (i1 icmp eq (i16* getelementptr inbounds (i16, i16* @g2, i64 1), i16* @g1) to float), float uitofp (i1 icmp eq (i16* getelementptr inbounds (i16, i16* @g2, i64 1), i16* @g1) to float)))
+  %fmul = fmul float uitofp (i1 icmp eq (i16* getelementptr inbounds (i16, i16* @g2, i64 1), i16* @g1) to float), uitofp (i1 icmp eq (i16* getelementptr inbounds (i16, i16* @g2, i64 1), i16* @g1) to float)
+  %call = call float @fabsf(float %fmul)
   ret float %call
 }