[llvm-commits] [llvm] r161452 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineCompares.cpp test/Transforms/InstCombine/2008-11-08-FCmp.ll

[Bob Wilson]

Author: bwilson
Date: Tue Aug  7 17:35:16 2012
New Revision: 161452

URL: http://llvm.org/viewvc/llvm-project?rev=161452&view=rev
Log:
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>

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/trunk/test/Transforms/InstCombine/2008-11-08-FCmp.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=161452&r1=161451&r2=161452&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Tue Aug  7 17:35:16 2012
@@ -2824,7 +2824,7 @@
       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;

Modified: llvm/trunk/test/Transforms/InstCombine/2008-11-08-FCmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/2008-11-08-FCmp.ll?rev=161452&r1=161451&r2=161452&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/2008-11-08-FCmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/2008-11-08-FCmp.ll Tue Aug  7 17:35:16 2012
@@ -45,3 +45,12 @@
   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
+}