Fix a serious typo in InstCombine's optimization of comparisons.

An unsigned value converted to floating-point will always be greater than
a negative constant.  Unfortunately InstCombine reversed the check so that
unsigned values were being optimized to always be greater than all positive
floating-point constants.  <rdar://problem/12029145>

llvm-svn: 161452

2 files changed, 10 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 7076d88554d..bdd310e97f6 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2824,7 +2824,7 @@ Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I,
       case ICmpInst::ICMP_UGE:
         // (float)int >= -4.4   --> true
         // (float)int >= 4.4    --> int > 4
-        if (!RHS.isNegative())
+        if (RHS.isNegative())
           return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext()));
         Pred = ICmpInst::ICMP_UGT;
         break;
diff --git a/llvm/test/Transforms/InstCombine/2008-11-08-FCmp.ll b/llvm/test/Transforms/InstCombine/2008-11-08-FCmp.ll
index c636288661b..f33a1f59f61 100644
--- a/llvm/test/Transforms/InstCombine/2008-11-08-FCmp.ll
+++ b/llvm/test/Transforms/InstCombine/2008-11-08-FCmp.ll
@@ -45,3 +45,12 @@ define i1 @test6(i32 %val) {
   ret i1 %2
 ; CHECK: ret i1 false
 }
+
+; Check that optimizing unsigned >= comparisons correctly distinguishes
+; positive and negative constants.  <rdar://problem/12029145>
+define i1 @test7(i32 %val) {
+  %1 = uitofp i32 %val to double
+  %2 = fcmp oge double %1, 3.200000e+00
+  ret i1 %2
+; CHECK: icmp ugt i32 %val, 3
+}