[llvm] r229063 - [InstCombine] Fix a bug when combining `icmp` from `ptrtoint`

[Michael Liao]

Author: hliao
Date: Thu Feb 12 22:51:26 2015
New Revision: 229063

URL: http://llvm.org/viewvc/llvm-project?rev=229063&view=rev
Log:
[InstCombine] Fix a bug when combining `icmp` from `ptrtoint`

- First, there's a crash when we try to combine that pointers into `icmp`
  directly by creating a `bitcast`, which is invalid if that two pointers are
  from different address spaces.

- It's not always appropriate to cast one pointer to another if they are from
  different address spaces as that is not no-op cast. Instead, we only combine
  `icmp` from `ptrtoint` if that two pointers are of the same address space.


Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/trunk/test/Transforms/InstCombine/cast_ptr.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=229063&r1=229062&r2=229063&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Thu Feb 12 22:51:26 2015
@@ -1931,14 +1931,17 @@ Instruction *InstCombiner::visitICmpInst
   if (DL && LHSCI->getOpcode() == Instruction::PtrToInt &&
       DL->getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth()) {
     Value *RHSOp = nullptr;
-    if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1))) {
+    if (PtrToIntOperator *RHSC = dyn_cast<PtrToIntOperator>(ICI.getOperand(1))) {
+      Value *RHSCIOp = RHSC->getOperand(0);
+      if (RHSCIOp->getType()->getPointerAddressSpace() ==
+          LHSCIOp->getType()->getPointerAddressSpace()) {
+        RHSOp = RHSC->getOperand(0);
+        // If the pointer types don't match, insert a bitcast.
+        if (LHSCIOp->getType() != RHSOp->getType())
+          RHSOp = Builder->CreateBitCast(RHSOp, LHSCIOp->getType());
+      }
+    } else if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1)))
       RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
-    } else if (PtrToIntInst *RHSC = dyn_cast<PtrToIntInst>(ICI.getOperand(1))) {
-      RHSOp = RHSC->getOperand(0);
-      // If the pointer types don't match, insert a bitcast.
-      if (LHSCIOp->getType() != RHSOp->getType())
-        RHSOp = Builder->CreateBitCast(RHSOp, LHSCIOp->getType());
-    }
 
     if (RHSOp)
       return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSOp);

Modified: llvm/trunk/test/Transforms/InstCombine/cast_ptr.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/cast_ptr.ll?rev=229063&r1=229062&r2=229063&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/cast_ptr.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/cast_ptr.ll Thu Feb 12 22:51:26 2015
@@ -3,6 +3,8 @@
 
 target datalayout = "p:32:32-p1:32:32-p2:16:16"
 
+ at global = global i8 0
+
 ; This shouldn't convert to getelementptr because the relationship
 ; between the arithmetic and the layout of allocated memory is
 ; entirely unknown.
@@ -47,10 +49,29 @@ define i1 @test2_as2_larger(i8 addrspace
   ret i1 %r
 }
 
+; These casts should not be folded away.
+; CHECK-LABEL: @test2_diff_as
+; CHECK: icmp sge i32 %i0, %i1
+define i1 @test2_diff_as(i8* %p, i8 addrspace(1)* %q) {
+  %i0 = ptrtoint i8* %p to i32
+  %i1 = ptrtoint i8 addrspace(1)* %q to i32
+  %r0 = icmp sge i32 %i0, %i1
+  ret i1 %r0
+}
+
+; These casts should not be folded away.
+; CHECK-LABEL: @test2_diff_as_global
+; CHECK: icmp sge i32 %i1
+define i1 @test2_diff_as_global(i8 addrspace(1)* %q) {
+  %i0 = ptrtoint i8* @global to i32
+  %i1 = ptrtoint i8 addrspace(1)* %q to i32
+  %r0 = icmp sge i32 %i1, %i0
+  ret i1 %r0
+}
+
 ; These casts should also be folded away.
 ; CHECK-LABEL: @test3(
 ; CHECK: icmp eq i8* %a, @global
- at global = global i8 0
 define i1 @test3(i8* %a) {
         %tmpa = ptrtoint i8* %a to i32
         %r = icmp eq i32 %tmpa, ptrtoint (i8* @global to i32)