[llvm-commits] [llvm] r134883 - in /llvm/trunk: lib/Transforms/InstCombine/InstructionCombining.cpp test/Transforms/InstCombine/getelementptr.ll

[Rafael Espindola]

Author: rafael
Date: Sun Jul 10 22:43:47 2011
New Revision: 134883

URL: http://llvm.org/viewvc/llvm-project?rev=134883&view=rev
Log:
Don't duplicate the work done by a gep into a "bitcast" if the gep has
more than one use.

Fixes PR10322.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
    llvm/trunk/test/Transforms/InstCombine/getelementptr.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp?rev=134883&r1=134882&r2=134883&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Sun Jul 10 22:43:47 2011
@@ -785,6 +785,14 @@
   // getelementptr instructions into a single instruction.
   //
   if (GEPOperator *Src = dyn_cast<GEPOperator>(PtrOp)) {
+
+    // If this GEP has only 0 indices, it is the same pointer as
+    // Src. If Src is not a trivial GEP too, don't combine
+    // the indices.
+    if (GEP.hasAllZeroIndices() && !Src->hasAllZeroIndices() &&
+        !Src->hasOneUse())
+      return 0;
+
     // Note that if our source is a gep chain itself that we wait for that
     // chain to be resolved before we perform this transformation.  This
     // avoids us creating a TON of code in some cases.

Modified: llvm/trunk/test/Transforms/InstCombine/getelementptr.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/getelementptr.ll?rev=134883&r1=134882&r2=134883&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/getelementptr.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/getelementptr.ll Sun Jul 10 22:43:47 2011
@@ -456,3 +456,19 @@
 ; CHECK: = sext i32 %n to i64
 ; CHECK: %A = getelementptr i32* %I, i64 %
 }
+
+; Test that we don't duplicate work when the second gep is a "bitcast".
+%pr10322_t = type { i8* }
+declare void @pr10322_f2(%pr10322_t*)
+declare void @pr10322_f3(i8**)
+define void @pr10322_f1(%pr10322_t* %foo) {
+entry:
+  %arrayidx8 = getelementptr inbounds %pr10322_t* %foo, i64 2
+  call void @pr10322_f2(%pr10322_t* %arrayidx8) nounwind
+  %tmp2 = getelementptr inbounds %pr10322_t* %arrayidx8, i64 0, i32 0
+  call void @pr10322_f3(i8** %tmp2) nounwind
+  ret void
+
+; CHECK: @pr10322_f1
+; CHECK: %tmp2 = getelementptr inbounds %pr10322_t* %arrayidx8, i64 0, i32 0
+}