[llvm-commits] [llvm] r136585 - in /llvm/trunk: lib/Transforms/InstCombine/InstructionCombining.cpp test/Transforms/InstCombine/getelementptr.ll

[Rafael Espindola]

Author: rafael
Date: Sat Jul 30 23:43:41 2011
New Revision: 136585

URL: http://llvm.org/viewvc/llvm-project?rev=136585&view=rev
Log:
Add a small gep optimization I noticed was missing while reading some IL.

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=136585&r1=136584&r2=136585&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Sat Jul 30 23:43:41 2011
@@ -737,7 +737,15 @@
   return Ty;
 }
 
-
+static bool shouldMergeGEPs(GEPOperator &GEP, GEPOperator &Src) {
+  // 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 false;
+  return true;
+}
 
 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
   SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end());
@@ -785,21 +793,15 @@
   // 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())
+    if (!shouldMergeGEPs(*cast<GEPOperator>(&GEP), *Src))
       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.
-    //
-    if (GetElementPtrInst *SrcGEP =
-          dyn_cast<GetElementPtrInst>(Src->getOperand(0)))
-      if (SrcGEP->getNumOperands() == 2)
+    if (GEPOperator *SrcGEP =
+          dyn_cast<GEPOperator>(Src->getOperand(0)))
+      if (SrcGEP->getNumOperands() == 2 && shouldMergeGEPs(*Src, *SrcGEP))
         return 0;   // Wait until our source is folded to completion.
 
     SmallVector<Value*, 8> Indices;

Modified: llvm/trunk/test/Transforms/InstCombine/getelementptr.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/getelementptr.ll?rev=136585&r1=136584&r2=136585&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/getelementptr.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/getelementptr.ll Sat Jul 30 23:43:41 2011
@@ -472,3 +472,23 @@
 ; CHECK: @pr10322_f1
 ; CHECK: %tmp2 = getelementptr inbounds %pr10322_t* %arrayidx8, i64 0, i32 0
 }
+
+; Test that we combine the last two geps in this sequence, before we
+; would wait for gep1 and gep2 to be combined and never combine 2 and 3.
+%three_gep_t = type {i32}
+%three_gep_t2 = type {%three_gep_t}
+
+define void @three_gep_f(%three_gep_t2* %x) {
+  %gep1 = getelementptr %three_gep_t2* %x, i64 2
+  call void @three_gep_h(%three_gep_t2* %gep1)
+  %gep2 = getelementptr %three_gep_t2* %gep1, i64 0, i32 0
+  %gep3 = getelementptr %three_gep_t* %gep2, i64 0, i32 0
+  call void @three_gep_g(i32* %gep3)
+
+; CHECK: @three_gep_f
+; CHECK: %gep3 = getelementptr %three_gep_t2* %gep1, i64 0, i32 0, i32 0
+  ret void
+}
+
+declare void @three_gep_g(i32*)
+declare void @three_gep_h(%three_gep_t2*)