[PATCH] D19268: [DAGCombiner] Do not remove the load of stored values when optimizations are disabled

[Marianne Mailhot-Sarrasin via llvm-commits]

mamai set the repository for this revision to rL LLVM.
mamai updated this revision to Diff 57203.
mamai added a comment.

Added a test case showing that the optimization is done in /O1 and not in /O0. Also added the fix to 2 test cases that were broken by this patch since the code generated changed slightly in /O0.


Repository:
  rL LLVM

http://reviews.llvm.org/D19268

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/ARM/alloc-no-stack-realign.ll
  test/CodeGen/ARM/dag-combine-ldst.ll
  test/CodeGen/SystemZ/swift-return.ll

Index: test/CodeGen/SystemZ/swift-return.ll
===================================================================
--- test/CodeGen/SystemZ/swift-return.ll
+++ test/CodeGen/SystemZ/swift-return.ll
@@ -49,10 +49,9 @@
 ; CHECK: a %r2, 172(%r15)
 ; CHECK: a %r2, 176(%r15)
 ; CHECK-O0-LABEL: test2:
-; CHECK-O0: la %[[REG1:r[0-9]+]], 168(%r15)
 ; CHECK-O0: st %r2, [[SPILL1:[0-9]+]](%r15)
-; CHECK-O0: lgr %r2, %[[REG1]]
 ; CHECK-O0: l %r3, [[SPILL1]](%r15)
+; CHECK-O0: la %r2, 168(%r15)
 ; CHECK-O0: brasl %r14, gen2
 ; CHECK-O0-DAG: l %r{{.*}}, 184(%r15)
 ; CHECK-O0-DAG: l %r{{.*}}, 180(%r15)
Index: test/CodeGen/ARM/dag-combine-ldst.ll
===================================================================
--- /dev/null
+++ test/CodeGen/ARM/dag-combine-ldst.ll
@@ -0,0 +1,34 @@
+; RUN: llc < %s -mtriple=arm-eabi -mattr=+v4t -O0 | FileCheck %s -check-prefix=CHECK_O0
+; RUN: llc < %s -mtriple=arm-eabi -mattr=+v4t -O1 | FileCheck %s -check-prefix=CHECK_O1
+
+; In /O0, the addition must not be eliminated. This happens when the load
+; and store are folded by the DAGCombiner. In /O1 and above, the optimization
+; must be executed.
+
+; CHECK_O0: add	r0, r0, #2
+; CHECK_O1-NOT: add	r0, r0, #2
+
+define i32 @main() #0 {
+  %1 = alloca i32, align 4
+  %2 = alloca i32, align 4
+  store i32 0, i32* %1, align 4
+  store i32 0, i32* %2, align 4
+  %3 = load i32, i32* %2, align 4
+  %4 = add nsw i32 %3, 2
+  store i32 %4, i32* %2, align 4
+  %5 = load i32, i32* %2, align 4
+  %6 = icmp eq i32 %5, 2
+  br i1 %6, label %7, label %8
+
+; <label>:7:                                      ; preds = %0
+  store i32 0, i32* %1, align 4
+  br label %9
+
+; <label>:8:                                      ; preds = %0
+  store i32 5, i32* %1, align 4
+  br label %9
+
+; <label>:9:                                      ; preds = %8, %7
+  %10 = load i32, i32* %1, align 4
+  ret i32 %10
+}
\ No newline at end of file
Index: test/CodeGen/ARM/alloc-no-stack-realign.ll
===================================================================
--- test/CodeGen/ARM/alloc-no-stack-realign.ll
+++ test/CodeGen/ARM/alloc-no-stack-realign.ll
@@ -21,8 +21,9 @@
 ; NO-REALIGN: vst1.64 {{{d[0-9]+, d[0-9]+}}}, [r[[R2]]:128]
 ; NO-REALIGN: add r[[R2:[0-9]+]], r[[R1]], #32
 ; NO-REALIGN: vst1.64 {{{d[0-9]+, d[0-9]+}}}, [r[[R2]]:128]
-; NO-REALIGN: vst1.32 {{{d[0-9]+, d[0-9]+}}}, [r[[R1]]:128]!
-; NO-REALIGN: vst1.64 {{{d[0-9]+, d[0-9]+}}}, [r[[R1]]:128]
+; NO-REALIGN: mov	r[[R3:[0-9]+]], r[[R1]]
+; NO-REALIGN: vst1.32 {{{d[0-9]+, d[0-9]+}}}, [r[[R3]]:128]!
+; NO-REALIGN: vst1.64 {{{d[0-9]+, d[0-9]+}}}, [r[[R3]]:128]
 
 ; NO-REALIGN: add r[[R2:[0-9]+]], r[[R0:0]], #48
 ; NO-REALIGN: vst1.64 {{{d[0-9]+, d[0-9]+}}}, [r[[R2]]:128]
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10087,7 +10087,8 @@
   // value.
   // TODO: Handle store large -> read small portion.
   // TODO: Handle TRUNCSTORE/LOADEXT
-  if (ISD::isNormalLoad(N) && !LD->isVolatile()) {
+  if (OptLevel != CodeGenOpt::None &&
+      ISD::isNormalLoad(N) && !LD->isVolatile()) {
     if (ISD::isNON_TRUNCStore(Chain.getNode())) {
       StoreSDNode *PrevST = cast<StoreSDNode>(Chain);
       if (PrevST->getBasePtr() == Ptr &&


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