[llvm] [CodeGen] Use temp symbol for MBBs (PR #95031)
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Wed Jun 12 03:48:21 PDT 2024
https://github.com/aengelke updated https://github.com/llvm/llvm-project/pull/95031
>From 36165ff9b87600635b3d708921390e3ddc2a4ee7 Mon Sep 17 00:00:00 2001
From: Alexis Engelke <engelke at in.tum.de>
Date: Mon, 10 Jun 2024 20:29:09 +0200
Subject: [PATCH] [CodeGen] Use temporary symbol for MBBs
Internal label names never occur in the symbol table, so when using an
object streamer, there's no point in constructing these names and then
adding them to hash tables -- they are never visible in the output.
It's not possible to reuse createTempSymbol, because on BPF has a
different prefix for globals and basic blocks right now.
---
llvm/include/llvm/MC/MCContext.h | 6 ++++++
llvm/lib/CodeGen/MachineBasicBlock.cpp | 16 ++++++++--------
llvm/lib/MC/MCContext.cpp | 12 ++++++++++++
.../AArch64/branch-relax-cross-section.mir | 4 ++--
llvm/test/CodeGen/BPF/objdump_cond_op.ll | 9 +++------
llvm/test/CodeGen/BPF/objdump_cond_op_2.ll | 6 ++----
6 files changed, 33 insertions(+), 20 deletions(-)
diff --git a/llvm/include/llvm/MC/MCContext.h b/llvm/include/llvm/MC/MCContext.h
index 72eae85467dc9..91b956a3aec60 100644
--- a/llvm/include/llvm/MC/MCContext.h
+++ b/llvm/include/llvm/MC/MCContext.h
@@ -458,6 +458,12 @@ class MCContext {
MCSymbol *createNamedTempSymbol();
MCSymbol *createNamedTempSymbol(const Twine &Name);
+ /// Get or create a symbol for a basic block. For non-always-emit symbols,
+ /// this behaves like createTempSymbol, except that it uses the
+ /// PrivateLabelPrefix instead of the PrivateGlobalPrefix. When AlwaysEmit is
+ /// true, behaves like getOrCreateSymbol, prefixed with PrivateLabelPrefix.
+ MCSymbol *createBlockSymbol(const Twine &Name, bool AlwaysEmit = false);
+
/// Create the definition of a directional local symbol for numbered label
/// (used for "1:" definitions).
MCSymbol *createDirectionalLocalSymbol(unsigned LocalLabelVal);
diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 16505f21f0aad..abf43e39ee9a6 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -80,10 +80,11 @@ MCSymbol *MachineBasicBlock::getSymbol() const {
}
CachedMCSymbol = Ctx.getOrCreateSymbol(MF->getName() + Suffix);
} else {
- const StringRef Prefix = Ctx.getAsmInfo()->getPrivateLabelPrefix();
- CachedMCSymbol = Ctx.getOrCreateSymbol(Twine(Prefix) + "BB" +
- Twine(MF->getFunctionNumber()) +
- "_" + Twine(getNumber()));
+ // If the block occurs as label in inline assembly, parsing the assembly
+ // needs an actual label name => set AlwaysEmit in these cases.
+ CachedMCSymbol = Ctx.createBlockSymbol(
+ "BB" + Twine(MF->getFunctionNumber()) + "_" + Twine(getNumber()),
+ /*AlwaysEmit=*/hasLabelMustBeEmitted());
}
}
return CachedMCSymbol;
@@ -104,10 +105,9 @@ MCSymbol *MachineBasicBlock::getEndSymbol() const {
if (!CachedEndMCSymbol) {
const MachineFunction *MF = getParent();
MCContext &Ctx = MF->getContext();
- auto Prefix = Ctx.getAsmInfo()->getPrivateLabelPrefix();
- CachedEndMCSymbol = Ctx.getOrCreateSymbol(Twine(Prefix) + "BB_END" +
- Twine(MF->getFunctionNumber()) +
- "_" + Twine(getNumber()));
+ CachedEndMCSymbol = Ctx.createBlockSymbol(
+ "BB_END" + Twine(MF->getFunctionNumber()) + "_" + Twine(getNumber()),
+ /*AlwaysEmit=*/false);
}
return CachedEndMCSymbol;
}
diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index 1590054717960..4c69ef79f2064 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -309,6 +309,18 @@ MCSymbol *MCContext::createNamedTempSymbol(const Twine &Name) {
return createSymbol(NameSV, true, false);
}
+MCSymbol *MCContext::createBlockSymbol(const Twine &Name, bool AlwaysEmit) {
+ if (AlwaysEmit)
+ return getOrCreateSymbol(MAI->getPrivateLabelPrefix() + Name);
+
+ if (!UseNamesOnTempLabels)
+ return createSymbolImpl(nullptr, /*IsTemporary=*/true);
+
+ SmallString<128> NameSV;
+ raw_svector_ostream(NameSV) << MAI->getPrivateLabelPrefix() << Name;
+ return createSymbol(NameSV, false, /*IsTemporary=*/true);
+}
+
MCSymbol *MCContext::createLinkerPrivateTempSymbol() {
return createLinkerPrivateSymbol("tmp");
}
diff --git a/llvm/test/CodeGen/AArch64/branch-relax-cross-section.mir b/llvm/test/CodeGen/AArch64/branch-relax-cross-section.mir
index f8f0b76f1c9ff..db88bf0044a5f 100644
--- a/llvm/test/CodeGen/AArch64/branch-relax-cross-section.mir
+++ b/llvm/test/CodeGen/AArch64/branch-relax-cross-section.mir
@@ -473,8 +473,8 @@ body: |
; INDIRECT-NEXT: successors: %bb.1
; INDIRECT-NEXT: liveins: $x16
; INDIRECT-NEXT: {{ $}}
- ; INDIRECT-NEXT: $[[SCAVENGED_REGISTER:x[0-9]+]] = ADRP target-flags(aarch64-page) <mcsymbol .LBB5_1>
- ; INDIRECT-NEXT: $[[SCAVENGED_REGISTER]] = ADDXri $[[SCAVENGED_REGISTER]], target-flags(aarch64-pageoff, aarch64-nc) <mcsymbol .LBB5_1>, 0
+ ; INDIRECT-NEXT: $[[SCAVENGED_REGISTER:x[0-9]+]] = ADRP target-flags(aarch64-page) <mcsymbol >
+ ; INDIRECT-NEXT: $[[SCAVENGED_REGISTER]] = ADDXri $[[SCAVENGED_REGISTER]], target-flags(aarch64-pageoff, aarch64-nc) <mcsymbol >, 0
; INDIRECT-NEXT: BR $[[SCAVENGED_REGISTER]]
bb.0.entry:
diff --git a/llvm/test/CodeGen/BPF/objdump_cond_op.ll b/llvm/test/CodeGen/BPF/objdump_cond_op.ll
index 4a4fa84376cc8..3b2e6c1922fc4 100644
--- a/llvm/test/CodeGen/BPF/objdump_cond_op.ll
+++ b/llvm/test/CodeGen/BPF/objdump_cond_op.ll
@@ -27,7 +27,7 @@ define i32 @test(i32, i32) local_unnamed_addr #0 {
br label %13
; CHECK: r1 <<= 32
; CHECK: r1 >>= 32
-; CHECK: if r1 != 2 goto +6 <LBB0_2>
+; CHECK: if r1 != 2 goto +6 <test+0x48>
; <label>:8: ; preds = %2
%9 = icmp eq i32 %0, %1
@@ -38,32 +38,29 @@ define i32 @test(i32, i32) local_unnamed_addr #0 {
; CHECK: r0 = *(u32 *)(r1 + 0)
; CHECK: r0 *= r0
; CHECK: r0 <<= 1
-; CHECK: goto +7 <LBB0_4>
+; CHECK: goto +7 <test+0x80>
; <label>:11: ; preds = %8
%12 = shl nsw i32 %10, 2
br label %13
-; CHECK-LABEL: <LBB0_2>:
; CHECK: r3 = 0 ll
; CHECK: r0 = *(u32 *)(r3 + 0)
; CHECK: r2 <<= 32
; CHECK: r2 >>= 32
-; CHECK: if r1 == r2 goto +4 <LBB0_5>
+; CHECK: if r1 == r2 goto +4 <test+0x98>
; CHECK: r0 <<= 2
; <label>:13: ; preds = %4, %11
%14 = phi i32 [ %12, %11 ], [ %7, %4 ]
store i32 %14, ptr @gbl, align 4
br label %15
-; CHECK-LABEL: <LBB0_4>:
; CHECK: r1 = 0 ll
; CHECK: *(u32 *)(r1 + 0) = r0
; <label>:15: ; preds = %8, %13
%16 = phi i32 [ %14, %13 ], [ %10, %8 ]
ret i32 %16
-; CHECK-LABEL: <LBB0_5>:
; CHECK: exit
}
attributes #0 = { norecurse nounwind }
diff --git a/llvm/test/CodeGen/BPF/objdump_cond_op_2.ll b/llvm/test/CodeGen/BPF/objdump_cond_op_2.ll
index 4edd52a463ea9..8c9e91d4a80ea 100644
--- a/llvm/test/CodeGen/BPF/objdump_cond_op_2.ll
+++ b/llvm/test/CodeGen/BPF/objdump_cond_op_2.ll
@@ -14,8 +14,7 @@ define i32 @test(i32, i32) local_unnamed_addr #0 {
; <label>:4: ; preds = %2
br label %5
-; CHECK: if r4 s>= r3 goto +10 <LBB0_2>
-; CHECK-LABEL: <LBB0_1>:
+; CHECK: if r4 s>= r3 goto +10 <test+0x90>
; <label>:5: ; preds = %4, %5
%6 = phi i32 [ %9, %5 ], [ 0, %4 ]
@@ -27,12 +26,11 @@ define i32 @test(i32, i32) local_unnamed_addr #0 {
%12 = icmp slt i32 %10, %11
br i1 %12, label %5, label %13
; CHECK: r1 = r3
-; CHECK: if r2 s> r3 goto -10 <LBB0_1>
+; CHECK: if r2 s> r3 goto -10 <test+0x40>
; <label>:13: ; preds = %5, %2
%14 = phi i32 [ 0, %2 ], [ %9, %5 ]
ret i32 %14
-; CHECK-LABEL: <LBB0_2>:
; CHECK: exit
}
attributes #0 = { norecurse nounwind readnone }
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