[cfe-commits] r51681 - in /cfe/trunk: lib/CodeGen/CGExprScalar.cpp test/CodeGen/pointer-cmp-type.c

[Eli Friedman]

Author: efriedma
Date: Thu May 29 10:09:15 2008
New Revision: 51681

URL: http://llvm.org/viewvc/llvm-project?rev=51681&view=rev
Log:
Fix an extremely subtle bug with pointer comparisons: they have to be 
unsigned because it's possible (at least in theory) to have
have both positive and negative pointers pointing to the same object.


Added:
    cfe/trunk/test/CodeGen/pointer-cmp-type.c
Modified:
    cfe/trunk/lib/CodeGen/CGExprScalar.cpp

Modified: cfe/trunk/lib/CodeGen/CGExprScalar.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprScalar.cpp?rev=51681&r1=51680&r2=51681&view=diff

==============================================================================
--- cfe/trunk/lib/CodeGen/CGExprScalar.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGExprScalar.cpp Thu May 29 10:09:15 2008
@@ -917,12 +917,12 @@
     if (LHS->getType()->isFloatingPoint()) {
       Result = Builder.CreateFCmp((llvm::FCmpInst::Predicate)FCmpOpc,
                                   LHS, RHS, "cmp");
-    } else if (LHSTy->isUnsignedIntegerType()) {
-      Result = Builder.CreateICmp((llvm::ICmpInst::Predicate)UICmpOpc,
+    } else if (LHSTy->isSignedIntegerType()) {
+      Result = Builder.CreateICmp((llvm::ICmpInst::Predicate)SICmpOpc,
                                   LHS, RHS, "cmp");
     } else {
-      // Signed integers and pointers.
-      Result = Builder.CreateICmp((llvm::ICmpInst::Predicate)SICmpOpc,
+      // Unsigned integers and pointers.
+      Result = Builder.CreateICmp((llvm::ICmpInst::Predicate)UICmpOpc,
                                   LHS, RHS, "cmp");
     }
   } else {

Added: cfe/trunk/test/CodeGen/pointer-cmp-type.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/pointer-cmp-type.c?rev=51681&view=auto

==============================================================================
--- cfe/trunk/test/CodeGen/pointer-cmp-type.c (added)
+++ cfe/trunk/test/CodeGen/pointer-cmp-type.c Thu May 29 10:09:15 2008
@@ -0,0 +1,3 @@
+// RUN: clang -emit-llvm %s -o - | grep "icmp ult"
+
+int a(char* a, char* b) {return a<b;}