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e0e599e202
CodeGenPrepare knows how to move a zext of a load into the same basic block where the load lives. The goal is to help ISel match a zero-extending load instead of two separated instructions. CGP attempts to move a zext computation even if it lives in a basic block that does not post-dominate the load's basic block. That means, the hoisted zext may be speculated. Preserving the zext location would hurt the debugging experience and the quality of sample pgo. With this patch, when moving a zext near to its associated load, CGP no longer propagates the zext's debug location. Instead, CGP conservatively reuses the same debug location for the load and the zext. An alternative approach would be to assign an artificial line-0 location to the zext. However we don't want to over-use the 'line-0' for this particular case because it would have a size cost in the line-table section for no additional benefit. Differential Revision: https://reviews.llvm.org/D25611 llvm-svn: 284377
72 lines
2.7 KiB
LLVM
72 lines
2.7 KiB
LLVM
; RUN: opt -S -codegenprepare < %s | FileCheck %s
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;
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; This test case was generated from the following source code:
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;
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; long long foo(int *ptr, int cond) {
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; long long result = 3;
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; unsigned val = *ptr; // line 3
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; switch (cond) {
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; case 3:
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; result = val; // line 6
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; break;
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; case 4:
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; result += 2;
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; }
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;
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; return result + val;
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; };
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;
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; When CGP moves a zext Z of a load L to the block where L lives, Z should not
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; retain its original debug location. Instead, Z should reuse the debug location
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; associated with L. Logically the zero extend will become part of the load; the
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; code generator will attempt to fuse the two instructions into a zextload.
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; CHECK-LABEL: @test
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; CHECK: [[LOADVAL:%[0-9]+]] = load i32, i32* %ptr, align 4, !dbg [[DEBUGLOC:![0-9]+]]
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; CHECK-NEXT: zext i32 [[LOADVAL]] to i64, !dbg [[DEBUGLOC]]
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; CHECK: [[DEBUGLOC]] = !DILocation(line: 3
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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define i64 @test(i32* %ptr, i32 %cond) !dbg !5 {
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entry:
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%0 = load i32, i32* %ptr, align 4, !dbg !7
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switch i32 %cond, label %sw.epilog [
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i32 3, label %sw.bb
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i32 4, label %sw.bb1
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], !dbg !8
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sw.bb: ; preds = %entry
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%conv = zext i32 %0 to i64, !dbg !9
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br label %sw.epilog, !dbg !10
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sw.bb1: ; preds = %entry
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br label %sw.epilog, !dbg !11
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sw.epilog: ; preds = %sw.bb1, %entry, %sw.bb
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%result.0 = phi i64 [ 3, %entry ], [ 5, %sw.bb1 ], [ %conv, %sw.bb ]
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%conv2 = zext i32 %0 to i64, !dbg !12
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%add3 = add nuw nsw i64 %result.0, %conv2, !dbg !13
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ret i64 %add3, !dbg !14
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}
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!3, !4}
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!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "", isOptimized: true, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
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!1 = !DIFile(filename: "test.c", directory: "")
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!2 = !{}
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!3 = !{i32 2, !"Dwarf Version", i32 4}
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!4 = !{i32 2, !"Debug Info Version", i32 3}
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!5 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 1, type: !6, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !2)
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!6 = !DISubroutineType(types: !2)
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!7 = !DILocation(line: 3, column: 18, scope: !5)
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!8 = !DILocation(line: 4, column: 3, scope: !5)
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!9 = !DILocation(line: 6, column: 14, scope: !5)
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!10 = !DILocation(line: 7, column: 5, scope: !5)
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!11 = !DILocation(line: 10, column: 3, scope: !5)
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!12 = !DILocation(line: 12, column: 19, scope: !5)
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!13 = !DILocation(line: 12, column: 17, scope: !5)
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!14 = !DILocation(line: 12, column: 3, scope: !5)
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