[llvm] r320758 - EmitFuncArgumentDbgValue: Prefer stack slots over registers for stack arguments
Adrian Prantl via llvm-commits
llvm-commits at lists.llvm.org
Thu Dec 14 14:55:06 PST 2017
Author: adrian
Date: Thu Dec 14 14:55:06 2017
New Revision: 320758
URL: http://llvm.org/viewvc/llvm-project?rev=320758&view=rev
Log:
EmitFuncArgumentDbgValue: Prefer stack slots over registers for stack arguments
While investigating LLVM PR22316 (http://llvm.org/bugs/show_bug.cgi?id=22316)
I started wondering if it were not always preferable to emit the
initial DBG_VALUEs for stack arguments as FI locations instead of
describing the first register they get copied into. The advantage of
doing this is that the arguments will be available as soon as the
stack is setup. As illustrated by the testcase in the PR, the first
copy of the FI into a register may be sunk by MachineSink.cpp into a
later basic block. By describing the argument on the stack, we nicely
circumvent this problem.
<rdar://problem/19583723>
Differential Revision: https://reviews.llvm.org/D41135
Added:
llvm/trunk/test/DebugInfo/X86/stack-args.ll
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=320758&r1=320757&r2=320758&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Thu Dec 14 14:55:06 2017
@@ -4854,6 +4854,13 @@ bool SelectionDAGBuilder::EmitFuncArgume
}
}
+ if (!Op && N.getNode())
+ // Check if frame index is available.
+ if (LoadSDNode *LNode = dyn_cast<LoadSDNode>(N.getNode()))
+ if (FrameIndexSDNode *FINode =
+ dyn_cast<FrameIndexSDNode>(LNode->getBasePtr().getNode()))
+ Op = MachineOperand::CreateFI(FINode->getIndex());
+
if (!Op) {
// Check if ValueMap has reg number.
DenseMap<const Value *, unsigned>::iterator VMI = FuncInfo.ValueMap.find(V);
@@ -4889,13 +4896,6 @@ bool SelectionDAGBuilder::EmitFuncArgume
}
}
- if (!Op && N.getNode())
- // Check if frame index is available.
- if (LoadSDNode *LNode = dyn_cast<LoadSDNode>(N.getNode()))
- if (FrameIndexSDNode *FINode =
- dyn_cast<FrameIndexSDNode>(LNode->getBasePtr().getNode()))
- Op = MachineOperand::CreateFI(FINode->getIndex());
-
if (!Op)
return false;
Added: llvm/trunk/test/DebugInfo/X86/stack-args.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/stack-args.ll?rev=320758&view=auto
==============================================================================
--- llvm/trunk/test/DebugInfo/X86/stack-args.ll (added)
+++ llvm/trunk/test/DebugInfo/X86/stack-args.ll Thu Dec 14 14:55:06 2017
@@ -0,0 +1,76 @@
+; RUN: llc -filetype=obj -o - %s | llvm-dwarfdump - | FileCheck %s
+; Generated from:
+; void * __attribute__ (( regparm(2) )) f(void *, void *);
+; void * __attribute__ (( regparm(0) )) g(void *, void *);
+;
+; void *g(void *t, void *k) {
+; if (k == (void *)0)
+; return (void *)0;
+; return f(t, k);
+; }
+
+; CHECK: DW_TAG_formal_parameter
+; CHECK-NEXT: DW_AT_location (DW_OP_fbreg +4)
+; CHECK-NEXT: DW_AT_name ("t")
+; CHECK: DW_TAG_formal_parameter
+; CHECK-NEXT: DW_AT_location (DW_OP_fbreg +8)
+; CHECK-NEXT: DW_AT_name ("k")
+
+source_filename = "t.c"
+target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i386--linux-gnu"
+
+; Function Attrs: nounwind
+define i8* @g(i8* %t, i8* %k) local_unnamed_addr #0 !dbg !10 {
+entry:
+ call void @llvm.dbg.value(metadata i8* %t, metadata !14, metadata !DIExpression()), !dbg !16
+ call void @llvm.dbg.value(metadata i8* %k, metadata !15, metadata !DIExpression()), !dbg !17
+ %cmp = icmp eq i8* %k, null, !dbg !18
+ br i1 %cmp, label %return, label %if.end, !dbg !20
+
+if.end: ; preds = %entry
+ %call = tail call i8* @f(i8* inreg %t, i8* inreg nonnull %k) #3, !dbg !21
+ br label %return, !dbg !22
+
+return: ; preds = %entry, %if.end
+ %retval.0 = phi i8* [ %call, %if.end ], [ null, %entry ]
+ ret i8* %retval.0, !dbg !23
+}
+
+declare i8* @f(i8* inreg, i8* inreg) local_unnamed_addr
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+attributes #0 = { nounwind }
+attributes #2 = { nounwind readnone speculatable }
+attributes #3 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!5, !6, !7, !8}
+!llvm.ident = !{!9}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 6.0.0 (llvm/trunk 319230)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3)
+!1 = !DIFile(filename: "t.c", directory: "/")
+!2 = !{}
+!3 = !{!4}
+!4 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 32)
+!5 = !{i32 1, !"NumRegisterParameters", i32 0}
+!6 = !{i32 2, !"Dwarf Version", i32 4}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = !{i32 1, !"wchar_size", i32 4}
+!9 = !{!"clang version 6.0.0 (llvm/trunk 319230)"}
+!10 = distinct !DISubprogram(name: "g", scope: !1, file: !1, line: 4, type: !11, isLocal: false, isDefinition: true, scopeLine: 4, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !13)
+!11 = !DISubroutineType(types: !12)
+!12 = !{!4, !4, !4}
+!13 = !{!14, !15}
+!14 = !DILocalVariable(name: "t", arg: 1, scope: !10, file: !1, line: 4, type: !4)
+!15 = !DILocalVariable(name: "k", arg: 2, scope: !10, file: !1, line: 4, type: !4)
+!16 = !DILocation(line: 4, column: 15, scope: !10)
+!17 = !DILocation(line: 4, column: 24, scope: !10)
+!18 = !DILocation(line: 5, column: 9, scope: !19)
+!19 = distinct !DILexicalBlock(scope: !10, file: !1, line: 5, column: 7)
+!20 = !DILocation(line: 5, column: 7, scope: !10)
+!21 = !DILocation(line: 7, column: 10, scope: !10)
+!22 = !DILocation(line: 7, column: 3, scope: !10)
+!23 = !DILocation(line: 8, column: 1, scope: !10)
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