[llvm] r218569 - [AArch64] Redundant store instructions should be removed as dead code
James Molloy
james.molloy at arm.com
Sat Sep 27 10:02:55 PDT 2014
Author: jamesm
Date: Sat Sep 27 12:02:54 2014
New Revision: 218569
URL: http://llvm.org/viewvc/llvm-project?rev=218569&view=rev
Log:
[AArch64] Redundant store instructions should be removed as dead code
If there is a store followed by a store with the same value to the same location, then the store is dead/noop. It can be removed.
This problem is found in spec2006-197.parser.
For example,
stur w10, [x11, #-4]
stur w10, [x11, #-4]
Then one of the two stur instructions can be removed.
Patch by David Xu!
Added:
llvm/trunk/test/CodeGen/AArch64/Redundantstore.ll
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=218569&r1=218568&r2=218569&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Sat Sep 27 12:02:54 2014
@@ -9858,6 +9858,17 @@ SDValue DAGCombiner::visitSTORE(SDNode *
}
}
+ // If this is a store followed by a store with the same value to the same
+ // location, then the store is dead/noop.
+ if (StoreSDNode *ST1 = dyn_cast<StoreSDNode>(Chain)) {
+ if (ST1->getBasePtr() == Ptr && ST->getMemoryVT() == ST1->getMemoryVT() &&
+ ST1->getValue() == Value && ST->isUnindexed() && !ST->isVolatile() &&
+ ST1->isUnindexed() && !ST1->isVolatile()) {
+ // The store is dead, remove it.
+ return Chain;
+ }
+ }
+
// If this is an FP_ROUND or TRUNC followed by a store, fold this into a
// truncating store. We can do this even if this is already a truncstore.
if ((Value.getOpcode() == ISD::FP_ROUND || Value.getOpcode() == ISD::TRUNCATE)
Added: llvm/trunk/test/CodeGen/AArch64/Redundantstore.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/Redundantstore.ll?rev=218569&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/Redundantstore.ll (added)
+++ llvm/trunk/test/CodeGen/AArch64/Redundantstore.ll Sat Sep 27 12:02:54 2014
@@ -0,0 +1,25 @@
+; RUN: llc -O3 -march=aarch64 < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+ at end_of_array = common global i8* null, align 8
+
+; CHECK-LABEL: @test
+; CHECK: stur
+; CHECK-NOT: stur
+define i8* @test(i32 %size) {
+entry:
+ %0 = load i8** @end_of_array, align 8
+ %conv = sext i32 %size to i64
+ %and = and i64 %conv, -8
+ %conv2 = trunc i64 %and to i32
+ %add.ptr.sum = add nsw i64 %and, -4
+ %add.ptr3 = getelementptr inbounds i8* %0, i64 %add.ptr.sum
+ %size4 = bitcast i8* %add.ptr3 to i32*
+ store i32 %conv2, i32* %size4, align 4
+ %add.ptr.sum9 = add nsw i64 %and, -4
+ %add.ptr5 = getelementptr inbounds i8* %0, i64 %add.ptr.sum9
+ %size6 = bitcast i8* %add.ptr5 to i32*
+ store i32 %conv2, i32* %size6, align 4
+ ret i8* %0
+}
+
More information about the llvm-commits
mailing list