[llvm] fc93ba0 - [GlobalISel][DebugInfo] Remove debug info with zero line from constants inserted at entry block
David Blaikie via llvm-commits
llvm-commits at lists.llvm.org
Mon Jul 25 10:19:15 PDT 2022
Author: Vladislav Dzhidzhoev
Date: 2022-07-25T17:19:01Z
New Revision: fc93ba061aa05a428057e7a7753128f27af0dd41
URL: https://github.com/llvm/llvm-project/commit/fc93ba061aa05a428057e7a7753128f27af0dd41
DIFF: https://github.com/llvm/llvm-project/commit/fc93ba061aa05a428057e7a7753128f27af0dd41.diff
LOG: [GlobalISel][DebugInfo] Remove debug info with zero line from constants inserted at entry block
Emission of constants having DebugLoc with line 0 causes significant increase of debug_line section size for some source files.
To illustrate, we can compare section sizes of several files from llvm test-suite, built with SelectionDAG vs GlobalISel, on Aarch64 (macOS), using -O0 optimization level:
| Source path | SDAG text sz | GISel text sz | SDAG debug_line sz | GISel debug_line sz
| -------------------------------------------------------------- | ------------ | ------------- | ------------------ | --------------------
| `SingleSource/Regression/C/gcc-c-torture/execute/strlen-2.c` | 15320 | 660 | 14872 | 6340
| `SingleSource/Regression/C/gcc-c-torture/execute/20040629-1.c` | 33640 | 26300 | 2812 | 6693
| `SingleSource/Benchmarks/Misc/flops-4.c` | 1428 | 1196 | 594 | 1008
| `MultiSource/Benchmarks/MiBench/consumer-typeset/z31.c` | 2716 | 964 | 809 | 903
| `MultiSource/Benchmarks/Prolangs-C/gnugo/showinst.c` | 2534 | 2502 | 189 | 573
For instance, here is a fragment of `flops-4.c.o` debug line section dump
```
Address Line Column File ISA Discriminator Flags
------------------ ------ ------ ------ --- ------------- -------------
0x0000000000000000 174 0 1 0 0 is_stmt
0x0000000000000010 0 0 1 0 0
0x0000000000000018 185 4 1 0 0 is_stmt prologue_end
0x000000000000001c 0 0 1 0 0
0x0000000000000024 186 4 1 0 0 is_stmt
0x000000000000002c 189 10 1 0 0 is_stmt
0x0000000000000030 0 0 1 0 0
0x0000000000000038 207 11 1 0 0 is_stmt
0x0000000000000044 208 11 1 0 0 is_stmt
0x0000000000000048 0 0 1 0 0
0x0000000000000058 210 10 1 0 0 is_stmt
0x000000000000005c 0 0 1 0 0
0x0000000000000060 211 10 1 0 0 is_stmt
0x0000000000000064 0 0 1 0 0
0x000000000000006c 212 10 1 0 0 is_stmt
0x0000000000000070 0 0 1 0 0
0x000000000000007c 213 10 1 0 0 is_stmt
0x0000000000000080 0 0 1 0 0
0x0000000000000088 214 10 1 0 0 is_stmt
0x000000000000008c 0 0 1 0 0
0x0000000000000094 215 10 1 0 0 is_stmt
```
Lot of zero lines are produced by constants (global values) having DebugLoc with line 0.
It seems that they're not significant for debugging experience.
With the commit applied, total size of debug_line sections of llvm shared libraries has reduced by 2.5%.
Change of debug line section size of files listed above:
| Source path | GISel debug_line sz | Patch debug_line sz
| -------------------------------------------------------------- | ------------------- | --------------------
| `SingleSource/Regression/C/gcc-c-torture/execute/strlen-2.c` | 6340 | 1465
| `SingleSource/Regression/C/gcc-c-torture/execute/20040629-1.c` | 6693 | 3782
| `SingleSource/Benchmarks/Misc/flops-4.c` | 1008 | 609
| `MultiSource/Benchmarks/MiBench/consumer-typeset/z31.c` | 903 | 841
| `MultiSource/Benchmarks/Prolangs-C/gnugo/showinst.c` | 573 | 190
Reviewed By: dblaikie
Differential Revision: https://reviews.llvm.org/D127488
Added:
Modified:
llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
llvm/test/CodeGen/AArch64/GlobalISel/combine-shift-of-shifted-dbg-value-fallback.ll
llvm/test/CodeGen/AArch64/GlobalISel/constant-dbg-loc.ll
Removed:
################################################################################
diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index dbdcfe0b6f0bb..2f9187bbf2ada 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -151,11 +151,11 @@ class DILocationVerifier : public GISelChangeObserver {
LLVM_DEBUG(dbgs() << "Checking DILocation from " << *CurrInst
<< " was copied to " << MI);
#endif
- // We allow insts in the entry block to have a debug loc line of 0 because
+ // We allow insts in the entry block to have no debug loc because
// they could have originated from constants, and we don't want a jumpy
// debug experience.
assert((CurrInst->getDebugLoc() == MI.getDebugLoc() ||
- MI.getDebugLoc().getLine() == 0) &&
+ (MI.getParent()->isEntryBlock() && !MI.getDebugLoc())) &&
"Line info was not transferred to all instructions");
}
};
@@ -3020,11 +3020,9 @@ bool IRTranslator::translate(const Instruction &Inst) {
bool IRTranslator::translate(const Constant &C, Register Reg) {
// We only emit constants into the entry block from here. To prevent jumpy
- // debug behaviour set the line to 0.
+ // debug behaviour remove debug line.
if (auto CurrInstDL = CurBuilder->getDL())
- EntryBuilder->setDebugLoc(DILocation::get(C.getContext(), 0, 0,
- CurrInstDL.getScope(),
- CurrInstDL.getInlinedAt()));
+ EntryBuilder->setDebugLoc(DebugLoc());
if (auto CI = dyn_cast<ConstantInt>(&C))
EntryBuilder->buildConstant(Reg, *CI);
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/combine-shift-of-shifted-dbg-value-fallback.ll b/llvm/test/CodeGen/AArch64/GlobalISel/combine-shift-of-shifted-dbg-value-fallback.ll
index eb41722839d82..5ea39d94bf6b6 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/combine-shift-of-shifted-dbg-value-fallback.ll
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/combine-shift-of-shifted-dbg-value-fallback.ll
@@ -54,12 +54,10 @@ define void @baz(i8* %arg) !dbg !6 {
; CHECK-NEXT: //DEBUG_VALUE: baz:3 <- undef
; CHECK-NEXT: .loc 1 4 1 prologue_end // tmp.ll:4:1
; CHECK-NEXT: lsl x8, x0, #4
-; CHECK-NEXT: .loc 1 0 0 is_stmt 0 // tmp.ll:0:0
; CHECK-NEXT: adrp x9, global+202752
; CHECK-NEXT: add x9, x9, :lo12:global+202752
-; CHECK-NEXT: .loc 1 4 1 // tmp.ll:4:1
; CHECK-NEXT: and x8, x8, #0x1ff0
-; CHECK-NEXT: .loc 1 5 1 is_stmt 1 // tmp.ll:5:1
+; CHECK-NEXT: .loc 1 5 1 // tmp.ll:5:1
; CHECK-NEXT: str xzr, [x9, x8]
; CHECK-NEXT: .loc 1 6 1 // tmp.ll:6:1
; CHECK-NEXT: ret
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/constant-dbg-loc.ll b/llvm/test/CodeGen/AArch64/GlobalISel/constant-dbg-loc.ll
index 0642e8bf83aca..8321b98f3f3f3 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/constant-dbg-loc.ll
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/constant-dbg-loc.ll
@@ -6,16 +6,16 @@ target triple = "arm64-apple-ios5.0.0"
@var1 = common global i32 0, align 4, !dbg !0
@var2 = common global i32 0, align 4, !dbg !6
-; We check here that the G_GLOBAL_VALUE has a debug loc with line 0.
+; We check here that the G_GLOBAL_VALUE has no debug loc.
define i32 @main() #0 !dbg !14 {
; CHECK-LABEL: name: main
; CHECK: bb.1.entry:
; CHECK: successors: %bb.2(0x40000000), %bb.3(0x40000000)
; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
- ; CHECK: [[GV:%[0-9]+]]:_(p0) = G_GLOBAL_VALUE @var1, debug-location !DILocation(line: 0, scope: !18)
+ ; CHECK: [[GV:%[0-9]+]]:_(p0) = G_GLOBAL_VALUE @var1
; CHECK: [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 1
; CHECK: [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 2
- ; CHECK: [[GV1:%[0-9]+]]:_(p0) = G_GLOBAL_VALUE @var2, debug-location !DILocation(line: 0, scope: !22)
+ ; CHECK: [[GV1:%[0-9]+]]:_(p0) = G_GLOBAL_VALUE @var2
; CHECK: [[FRAME_INDEX:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.0.retval
; CHECK: G_STORE [[C]](s32), [[FRAME_INDEX]](p0) :: (store (s32) into %ir.retval)
; CHECK: [[LOAD:%[0-9]+]]:_(s32) = G_LOAD [[GV]](p0), debug-location !17 :: (dereferenceable load (s32) from @var1)
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