[PATCH] D115808: [DAGCombiner] Avoid combining adjacent stores at -O0 to improve debug experience

[Shivam Gupta via Phabricator via llvm-commits]

xgupta updated this revision to Diff 395105.
xgupta added a comment.
Herald added a subscriber: ormris.

Address comments


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D115808/new/

https://reviews.llvm.org/D115808

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/RISCV/dbg-combine.ll


Index: llvm/test/CodeGen/RISCV/dbg-combine.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/RISCV/dbg-combine.ll
@@ -0,0 +1,69 @@
+; RUN: llc -mtriple=riscv64 -verify-machineinstrs < %s | FileCheck %s
+
+; Make sure that the sequence of debug locations for function foo is correctly
+; generated. More specifically, .loc entries for lines 6 and 7 must appear in
+; the correct sequence.
+
+; $ clang -emit-llvm -S -g dbg-combine.c
+; 1 int main ()
+; 2 {
+; 3   int size;
+; 4
+; 5   size = (int) sizeof (long long);
+; 6   size = (int) sizeof (void*);
+; 7   size = (int) sizeof (void (*)(void));
+; 8
+; 9   return 0;
+; 10 }
+
+; CHECK: .loc    1 6
+; CHECK: .loc    1 7
+
+; ModuleID = 'dbg-combine.c'
+source_filename = "dbg-combine.c"
+target datalayout = "e-m:e-p:64:64-i64:64-i128:128-n64-S128"
+target triple = "riscv64-unknown-unknown-elf"
+
+; Function Attrs: noinline nounwind optnone
+define dso_local signext i32 @main() #0 !dbg !11 {
+entry:
+  %retval = alloca i32, align 4
+  %size = alloca i32, align 4
+  store i32 0, i32* %retval, align 4
+  call void @llvm.dbg.declare(metadata i32* %size, metadata !14, metadata !DIExpression()), !dbg !15
+  store i32 8, i32* %size, align 4, !dbg !16
+  store i32 8, i32* %size, align 4, !dbg !17
+  store i32 8, i32* %size, align 4, !dbg !18
+  ret i32 0, !dbg !19
+}
+
+; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+attributes #0 = { noinline nounwind optnone "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+64bit,+a,+c,+m,+relax,-save-restore" }
+attributes #1 = { nofree nosync nounwind readnone speculatable willreturn }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!4, !5, !6, !7, !8, !9}
+!llvm.ident = !{!10}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 14.0.0 (https://github.com/llvm/llvm-project.git ecfd2d2403ae336195de7cdb06e1fe02a2bf1bc9)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, retainedTypes: !2, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "dbg-combine.c", directory: "/home/xgupta/riscv/riscv-llvm/_build/bin")
+!2 = !{!3}
+!3 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!4 = !{i32 7, !"Dwarf Version", i32 4}
+!5 = !{i32 2, !"Debug Info Version", i32 3}
+!6 = !{i32 1, !"wchar_size", i32 4}
+!7 = !{i32 1, !"target-abi", !"lp64"}
+!8 = !{i32 7, !"frame-pointer", i32 2}
+!9 = !{i32 1, !"SmallDataLimit", i32 8}
+!10 = !{!"clang version 14.0.0 (https://github.com/llvm/llvm-project.git ecfd2d2403ae336195de7cdb06e1fe02a2bf1bc9)"}
+!11 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 1, type: !12, scopeLine: 2, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !13)
+!12 = !DISubroutineType(types: !2)
+!13 = !{}
+!14 = !DILocalVariable(name: "size", scope: !11, file: !1, line: 3, type: !3)
+!15 = !DILocation(line: 3, column: 7, scope: !11)
+!16 = !DILocation(line: 5, column: 8, scope: !11)
+!17 = !DILocation(line: 6, column: 8, scope: !11)
+!18 = !DILocation(line: 7, column: 8, scope: !11)
+!19 = !DILocation(line: 9, column: 3, scope: !11)
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -18280,8 +18280,8 @@
   if (StoreSDNode *ST1 = dyn_cast<StoreSDNode>(Chain)) {
     if (ST->isUnindexed() && ST->isSimple() &&
         ST1->isUnindexed() && ST1->isSimple()) {
-      if (ST1->getBasePtr() == Ptr && ST1->getValue() == Value &&
-          ST->getMemoryVT() == ST1->getMemoryVT() &&
+      if (OptLevel != CodeGenOpt::None && ST1->getBasePtr() == Ptr &&
+          ST1->getValue() == Value && ST->getMemoryVT() == ST1->getMemoryVT() &&
           ST->getAddressSpace() == ST1->getAddressSpace()) {
         // If this is a store followed by a store with the same value to the
         // same location, then the store is dead/noop.


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