[llvm-commits] [llvm] r160874 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineSelect.cpp test/Transforms/InstCombine/select-crash.ll

[Nuno Lopes]

Author: nlopes
Date: Fri Jul 27 13:03:57 2012
New Revision: 160874

URL: http://llvm.org/viewvc/llvm-project?rev=160874&view=rev
Log:
fix infinite loop in instcombine in the presence of a (malformed) self-referencing select inst.
This can happen as long as the instruction is not reachable. Instcombine does generate these unreachable malformed selects when doing RAUW

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
    llvm/trunk/test/Transforms/InstCombine/select-crash.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp?rev=160874&r1=160873&r2=160874&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp Fri Jul 27 13:03:57 2012
@@ -881,12 +881,16 @@
 
   if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) {
     if (TrueSI->getCondition() == CondVal) {
+      if (SI.getTrueValue() == TrueSI->getTrueValue())
+        return 0;
       SI.setOperand(1, TrueSI->getTrueValue());
       return &SI;
     }
   }
   if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) {
     if (FalseSI->getCondition() == CondVal) {
+      if (SI.getFalseValue() == FalseSI->getFalseValue())
+        return 0;
       SI.setOperand(2, FalseSI->getFalseValue());
       return &SI;
     }

Modified: llvm/trunk/test/Transforms/InstCombine/select-crash.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/select-crash.ll?rev=160874&r1=160873&r2=160874&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/select-crash.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/select-crash.ll Fri Jul 27 13:03:57 2012
@@ -30,3 +30,20 @@
   %sel = select i1 %b, <4 x float> %a, <4 x float> %sub 
   ret <4 x float> %sel
 }
+
+; CHECK: @test3
+define i32 @test3(i1 %bool, i32 %a) {
+entry:
+  %cond = or i1 %bool, true
+  br i1 %cond, label %return, label %xpto
+
+; technically reachable, but this malformed IR may appear as a result of constant propagation
+xpto:
+  %select = select i1 %bool, i32 %a, i32 %select
+  %select2 = select i1 %bool, i32 %select2, i32 %a
+  %sum = add i32 %select, %select2
+  ret i32 %sum
+
+return:
+  ret i32 7
+}