From: Sanjay Patel <spatel@rotateright.com>
Date: Tue, 26 Dec 2017 22:12:20 +0000 (+0000)
Subject: [InstCombine] fix miscompile of frem with 0.0 operand (PR34870)
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f186f082c569f37f10f8ef73ecad4b27d9359cab;p=llvm

[InstCombine] fix miscompile of frem with 0.0 operand (PR34870)

We might want to select NAN here or do this transform with fast-math,
but this should at least fix the miscompile.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321461 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 87666360c1a..541dde6c47d 100644
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1631,9 +1631,5 @@ Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
                                   SQ.getWithInstruction(&I)))
     return replaceInstUsesWith(I, V);
 
-  // Handle cases involving: rem X, (select Cond, Y, Z)
-  if (simplifyDivRemOfSelectWithZeroOp(I))
-    return &I;
-
   return nullptr;
 }
diff --git a/test/Transforms/InstCombine/rem.ll b/test/Transforms/InstCombine/rem.ll
index 348190df5b1..f71a0fb4c62 100644
--- a/test/Transforms/InstCombine/rem.ll
+++ b/test/Transforms/InstCombine/rem.ll
@@ -594,11 +594,12 @@ define <2 x i32> @test23(<2 x i32> %A) {
   ret <2 x i32> %mul
 }
 
-; FIXME: FP division-by-zero is not UB.
+; FP division-by-zero is not UB.
 
 define double @PR34870(i1 %cond, double %x, double %y) {
 ; CHECK-LABEL: @PR34870(
-; CHECK-NEXT:    [[FMOD:%.*]] = frem double %x, %y
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 %cond, double %y, double 0.000000e+00
+; CHECK-NEXT:    [[FMOD:%.*]] = frem double %x, [[SEL]]
 ; CHECK-NEXT:    ret double [[FMOD]]
 ;
   %sel = select i1 %cond, double %y, double 0.0