[PATCH] Branch folding causes different code generation at "-O2 -g" and "-O2"
Katya Romanova
Katya_Romanova at playstation.sony.com
Fri Mar 7 01:31:32 PST 2014
- it has been built and tested against trunk at 203176 (Mar6)
- debug info has been reduced a lot (thanks to Trevor's script that strips away unneeded debug info). Generating null metadata with stub debug_value calls resulted in an assertion, so I kept minimal metadata (7 entries only).
- BZ#19051 was replaced with http://llvm.org/PR19051
- the test case was checked with -mcpu=atom
Let me know if more corrections are needed or if it's OK to commit.
Hi chandlerc,
http://llvm-reviews.chandlerc.com/D2970
CHANGE SINCE LAST DIFF
http://llvm-reviews.chandlerc.com/D2970?vs=7563&id=7626#toc
Files:
lib/CodeGen/BranchFolding.cpp
test/CodeGen/X86/dbg-changes-codegen-branch-folding.ll
Index: lib/CodeGen/BranchFolding.cpp
===================================================================
--- lib/CodeGen/BranchFolding.cpp
+++ lib/CodeGen/BranchFolding.cpp
@@ -1515,7 +1515,7 @@
// branch from condition setting instruction.
MachineBasicBlock::iterator PI = Loc;
--PI;
- while (PI != MBB->begin() && Loc->isDebugValue())
+ while (PI != MBB->begin() && PI->isDebugValue())
--PI;
bool IsDef = false;
Index: test/CodeGen/X86/dbg-changes-codegen-branch-folding.ll
===================================================================
--- test/CodeGen/X86/dbg-changes-codegen-branch-folding.ll
+++ test/CodeGen/X86/dbg-changes-codegen-branch-folding.ll
@@ -0,0 +1,109 @@
+; RUN: llc -march=x86-64 < %s | FileCheck %s
+; RUN: opt -strip-debug < %s | llc -march=x86-64 | FileCheck %s
+; http://llvm.org/PR19051. Minor code-motion difference with -g.
+; Presence of debug info shouldn't affect the codegen. Make sure that
+; we generated the same code sequence with and without debug info.
+;
+; CHECK: callq _Z3fooPcjPKc
+; CHECK: callq _Z3fooPcjPKc
+; CHECK: leaq (%rsp), %rdi
+; CHECK: movl $4, %esi
+; CHECK: testl {{%[a-z]+}}, {{%[a-z]+}}
+; CHECK: je .LBB0_4
+
+; Regenerate test with this command:
+; clang -emit-llvm -S -O2 -g
+; from this source:
+;
+; extern void foo(char *dst,unsigned siz,const char *src);
+; extern const char * i2str(int);
+;
+; struct AAA3 {
+; AAA3(const char *value) { foo(text,sizeof(text),value);}
+; void operator=(const char *value) { foo(text,sizeof(text),value);}
+; operator const char*() const { return text;}
+; char text[4];
+; };
+;
+; void bar (int param1,int param2) {
+; const char * temp(0);
+;
+; if (param2) {
+; temp = i2str(param2);
+; }
+; AAA3 var1("");
+; AAA3 var2("");
+;
+; if (param1)
+; var2 = "+";
+; else
+; var2 = "-";
+; var1 = "";
+; }
+
+%struct.AAA3 = type { [4 x i8] }
+
+ at .str = private unnamed_addr constant [1 x i8] zeroinitializer, align 1
+ at .str1 = private unnamed_addr constant [2 x i8] c"+\00", align 1
+ at .str2 = private unnamed_addr constant [2 x i8] c"-\00", align 1
+
+; Function Attrs: uwtable
+define void @_Z3barii(i32 %param1, i32 %param2) #0 {
+entry:
+ %var1 = alloca %struct.AAA3, align 1
+ %var2 = alloca %struct.AAA3, align 1
+ %tobool = icmp eq i32 %param2, 0
+ br i1 %tobool, label %if.end, label %if.then
+
+if.then: ; preds = %entry
+ %call = call i8* @_Z5i2stri(i32 %param2)
+ br label %if.end
+
+if.end: ; preds = %entry, %if.then
+ call void @llvm.dbg.value(metadata !{%struct.AAA3* %var1}, i64 0, metadata !60)
+ call void @llvm.dbg.value(metadata !62, i64 0, metadata !63)
+ %arraydecay.i = getelementptr inbounds %struct.AAA3* %var1, i64 0, i32 0, i64 0
+ call void @_Z3fooPcjPKc(i8* %arraydecay.i, i32 4, i8* getelementptr inbounds ([1 x i8]* @.str, i64 0, i64 0))
+ call void @llvm.dbg.declare(metadata !{%struct.AAA3* %var2}, metadata !38)
+ %arraydecay.i5 = getelementptr inbounds %struct.AAA3* %var2, i64 0, i32 0, i64 0
+ call void @_Z3fooPcjPKc(i8* %arraydecay.i5, i32 4, i8* getelementptr inbounds ([1 x i8]* @.str, i64 0, i64 0))
+ %tobool1 = icmp eq i32 %param1, 0
+ br i1 %tobool1, label %if.else, label %if.then2
+
+if.then2: ; preds = %if.end
+ call void @_Z3fooPcjPKc(i8* %arraydecay.i5, i32 4, i8* getelementptr inbounds ([2 x i8]* @.str1, i64 0, i64 0))
+ br label %if.end3
+
+if.else: ; preds = %if.end
+ call void @_Z3fooPcjPKc(i8* %arraydecay.i5, i32 4, i8* getelementptr inbounds ([2 x i8]* @.str2, i64 0, i64 0))
+ br label %if.end3
+
+if.end3: ; preds = %if.else, %if.then2
+ call void @_Z3fooPcjPKc(i8* %arraydecay.i, i32 4, i8* getelementptr inbounds ([1 x i8]* @.str, i64 0, i64 0))
+ ret void
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata) #1
+
+declare i8* @_Z5i2stri(i32) #2
+
+declare void @_Z3fooPcjPKc(i8*, i32, i8*) #2
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata) #1
+
+attributes #0 = { uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+attributes #2 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.module.flags = !{!48, !49}
+!llvm.ident = !{!50}
+
+!38 = metadata !{i32 786688, null, metadata !"var2", null, i32 20, null, i32 0, i32 0} ; [ DW_TAG_auto_variable ] [var2] [line 20]
+!48 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
+!49 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!50 = metadata !{metadata !"clang version 3.5 (202418)"}
+!60 = metadata !{i32 786689, null, metadata !"this", null, i32 16777216, null, i32 1088, null} ; [ DW_TAG_arg_variable ] [this] [line 0]
+!62 = metadata !{i8* getelementptr inbounds ([1 x i8]* @.str, i64 0, i64 0)}
+!63 = metadata !{i32 786689, null, metadata !"value", null, i32 33554439, null, i32 0, null} ; [ DW_TAG_arg_variable ] [value] [line 7]
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