From 0891d752a68a25025ffc3339aab1f0ad3221b0ed Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Wed, 10 Mar 2010 19:31:51 +0000 Subject: [PATCH] Constant-fold GEP-of-GEP into a single GEP. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98178 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/ConstantFolding.cpp | 11 +++++++++++ test/Other/constant-fold-gep.ll | 31 +++++++++++++++++++++++++++++++ 2 files changed, 42 insertions(+) diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp index 114db2d3705..62020afb723 100644 --- a/lib/Analysis/ConstantFolding.cpp +++ b/lib/Analysis/ConstantFolding.cpp @@ -589,6 +589,17 @@ static Constant *SymbolicallyEvaluateGEP(Constant *const *Ops, unsigned NumOps, APInt Offset = APInt(BitWidth, TD->getIndexedOffset(Ptr->getType(), (Value**)Ops+1, NumOps-1)); + + // If this is a GEP of a GEP, fold it all into a single GEP. + while (GEPOperator *GEP = dyn_cast(Ptr)) { + SmallVector NestedOps(GEP->op_begin()+1, GEP->op_end()); + Ptr = cast(GEP->getOperand(0)); + Offset += APInt(BitWidth, + TD->getIndexedOffset(Ptr->getType(), + (Value**)NestedOps.data(), + NestedOps.size())); + } + // If the base value for this address is a literal integer value, fold the // getelementptr to the resulting integer value casted to the pointer type. if (BaseIsInt) { diff --git a/test/Other/constant-fold-gep.ll b/test/Other/constant-fold-gep.ll index 650b4af139e..ecef9c48492 100644 --- a/test/Other/constant-fold-gep.ll +++ b/test/Other/constant-fold-gep.ll @@ -21,10 +21,12 @@ ; PLAIN: %1 = type { double, float, double, double } ; PLAIN: %2 = type { i1, i1* } ; PLAIN: %3 = type { i64, i64 } +; PLAIN: %4 = type { i32, i32 } ; OPT: %0 = type { i1, double } ; OPT: %1 = type { double, float, double, double } ; OPT: %2 = type { i1, i1* } ; OPT: %3 = type { i64, i64 } +; OPT: %4 = type { i32, i32 } ; The automatic constant folder in opt does not have targetdata access, so ; it can't fold gep arithmetic, in general. However, the constant folder run @@ -122,6 +124,16 @@ @N = constant i64* getelementptr ({ i64, i64 }* null, i32 0, i32 1) @O = constant i64* getelementptr ([2 x i64]* null, i32 0, i32 1) +; Fold GEP of a GEP. Theoretically some of these cases could be folded +; without using targetdata, however that's not implemented yet. + +; PLAIN: @Z = global i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x %4]* @ext, i64 0, i64 1, i32 0), i64 1) +; OPT: @Z = global i32* getelementptr (i32* getelementptr inbounds ([3 x %4]* @ext, i64 0, i64 1, i32 0), i64 1) +; TO: @Z = global i32* getelementptr inbounds ([3 x %0]* @ext, i64 0, i64 1, i32 1) + +@ext = external global [3 x { i32, i32 }] +@Z = global i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x { i32, i32 }]* @ext, i64 0, i64 1, i32 0), i64 1) + ; Duplicate all of the above as function return values rather than ; global initializers. @@ -468,3 +480,22 @@ define i64* @fO() nounwind { %t = bitcast i64* getelementptr ([2 x i64]* null, i32 0, i32 1) to i64* ret i64* %t } + +; PLAIN: define i32* @fZ() nounwind { +; PLAIN: %t = bitcast i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x %4]* @ext, i64 0, i64 1, i32 0), i64 1) to i32* +; PLAIN: ret i32* %t +; PLAIN: } +; OPT: define i32* @fZ() nounwind { +; OPT: ret i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x %4]* @ext, i64 0, i64 1, i32 0), i64 1) +; OPT: } +; TO: define i32* @fZ() nounwind { +; TO: ret i32* getelementptr inbounds ([3 x %0]* @ext, i64 0, i64 1, i32 1) +; TO: } +; SCEV: Classifying expressions for: @fZ +; SCEV: %t = bitcast i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x %4]* @ext, i64 0, i64 1, i32 0), i64 1) to i32* +; SCEV: --> ((3 * sizeof(i32)) + @ext) + +define i32* @fZ() nounwind { + %t = bitcast i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x { i32, i32 }]* @ext, i64 0, i64 1, i32 0), i64 1) to i32* + ret i32* %t +}