[llvm] r354380 - [ConstantFold] Fix misfolding of icmp with a bitcast FP second operand.

[Andrew Scheidecker via llvm-commits]

Author: andrewscheidecker
Date: Tue Feb 19 13:03:20 2019
New Revision: 354380

URL: http://llvm.org/viewvc/llvm-project?rev=354380&view=rev
Log:
[ConstantFold] Fix misfolding of icmp with a bitcast FP second operand.

In the process of trying to eliminate the bitcast, this was producing a
malformed icmp with FP operands.

Differential revision: https://reviews.llvm.org/D51215


Modified:
    llvm/trunk/lib/IR/ConstantFold.cpp
    llvm/trunk/test/Transforms/ConstProp/bitcast.ll

Modified: llvm/trunk/lib/IR/ConstantFold.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/ConstantFold.cpp?rev=354380&r1=354379&r2=354380&view=diff
==============================================================================
--- llvm/trunk/lib/IR/ConstantFold.cpp (original)
+++ llvm/trunk/lib/IR/ConstantFold.cpp Tue Feb 19 13:03:20 2019
@@ -1980,11 +1980,13 @@ Constant *llvm::ConstantFoldCompareInstr
 
     // If the right hand side is a bitcast, try using its inverse to simplify
     // it by moving it to the left hand side.  We can't do this if it would turn
-    // a vector compare into a scalar compare or visa versa.
+    // a vector compare into a scalar compare or visa versa, or if it would turn
+    // the operands into FP values.
     if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
       Constant *CE2Op0 = CE2->getOperand(0);
       if (CE2->getOpcode() == Instruction::BitCast &&
-          CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) {
+          CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy() &&
+          !CE2Op0->getType()->isFPOrFPVectorTy()) {
         Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
         return ConstantExpr::getICmp(pred, Inverse, CE2Op0);
       }

Modified: llvm/trunk/test/Transforms/ConstProp/bitcast.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/ConstProp/bitcast.ll?rev=354380&r1=354379&r2=354380&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/ConstProp/bitcast.ll (original)
+++ llvm/trunk/test/Transforms/ConstProp/bitcast.ll Tue Feb 19 13:03:20 2019
@@ -10,19 +10,32 @@ define <1 x i64> @test1() {
   ret <1 x i64> %A
 }
 
-; FIXME: Don't try to propagate an FP source operand to an icmp.
+; Ensure that a FP source operand isn't propagated to an icmp.
 
 @a = external global i16, align 1
 @b = external global i16, align 1
 
 define i1 @bad_icmp_constexpr_bitcast() {
 ; CHECK-LABEL: @bad_icmp_constexpr_bitcast(
-; CHECK-NEXT:    ret i1 icmp eq (float bitcast (i32 ptrtoint (i16* @a to i32) to float), float fadd (float bitcast (i32 ptrtoint (i16* @b to i32) to float), float 2.000000e+00))
+; CHECK-NEXT:    ret i1 icmp eq (i32 ptrtoint (i16* @a to i32), i32 bitcast (float fadd (float bitcast (i32 ptrtoint (i16* @b to i32) to float), float 2.000000e+00) to i32))
 ;
   %cmp = icmp eq i32 ptrtoint (i16* @a to i32), bitcast (float fadd (float bitcast (i32 ptrtoint (i16* @b to i32) to float), float 2.0) to i32)
   ret i1 %cmp
 }
 
+; Ensure that an integer source operand isn't propagated to a fcmp.
+
+ at c = external global i16, align 1
+ at d = external global i16, align 1
+
+define i1 @bad_fcmp_constexpr_bitcast() {
+; CHECK-LABEL: @bad_fcmp_constexpr_bitcast(
+; CHECK-NEXT:    ret i1 fcmp oeq (float bitcast (i32 ptrtoint (i16* @c to i32) to float), float bitcast (i32 add (i32 ptrtoint (i16* @d to i32), i32 2) to float))
+;
+  %cmp = fcmp oeq float bitcast (i32 ptrtoint (i16* @c to i32) to float), bitcast (i32 add (i32 ptrtoint (i16* @d to i32), i32 2) to float)
+  ret i1 %cmp
+}
+
 ; FIXME: If the bitcasts result in a NaN FP value, then "ordered and equal" would be false.
 
 define i1 @fcmp_constexpr_oeq(float %conv) {