[SPARC] Prevent meta instructions from being inserted into delay slots #161111
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
Do not move instructions with generic opcodes like `FAKE_USE`/`@llvm.fake.use` into delay slots, as they are not real machine instructions. This should fix crashes when running `clang -Og`.
Member
| @llvm/pr-subscribers-backend-sparc Author: Koakuma (koachan) ChangesDo not move instructions with generic opcodes like This should fix crashes when compiling with, for example, Full diff: https://github.com/llvm/llvm-project/pull/161111.diff 2 Files Affected:
diff --git a/llvm/lib/Target/Sparc/DelaySlotFiller.cpp b/llvm/lib/Target/Sparc/DelaySlotFiller.cpp index 6c19049a001cf..73d03fc271100 100644 --- a/llvm/lib/Target/Sparc/DelaySlotFiller.cpp +++ b/llvm/lib/Target/Sparc/DelaySlotFiller.cpp @@ -206,8 +206,8 @@ Filler::findDelayInstr(MachineBasicBlock &MBB, if (!done) --I; - // skip debug instruction - if (I->isDebugInstr()) + // Skip debug and generic instructions. + if (I->isDebugInstr() || (I->getOpcode() <= TargetOpcode::GENERIC_OP_END)) continue; if (I->hasUnmodeledSideEffects() || I->isInlineAsm() || I->isPosition() || diff --git a/llvm/test/CodeGen/SPARC/2011-01-19-DelaySlot.ll b/llvm/test/CodeGen/SPARC/2011-01-19-DelaySlot.ll index 9ccd4f1c0ac9a..d4b21b248d60d 100644 --- a/llvm/test/CodeGen/SPARC/2011-01-19-DelaySlot.ll +++ b/llvm/test/CodeGen/SPARC/2011-01-19-DelaySlot.ll @@ -184,4 +184,30 @@ entry: ret i32 %2 } +define i32 @test_generic_inst(i32 %a) #0 { +;CHECK-LABEL: test_generic_inst: +;CHECK: ! fake_use: {{.*}} +;CHECK: bne {{.*}} +;CHECK-NEXT: nop + +%2 = call i32 @bar(i32 %a) + %3 = and i32 %2, 1 + %4 = icmp eq i32 %3, 0 + ; This shouldn't get reordered into a delay slot + call void (...) @llvm.fake.use(i32 %a) + br i1 %4, label %5, label %7 +5: + %6 = call i32 @bar(i32 %2) + br label %9 + +7: + %8 = add nsw i32 %2, 1 + br label %9 + +9: + %10 = phi i32 [ %6, %5 ], [ %8, %7 ] + ret i32 %10 +} + +declare void @llvm.fake.use(...) attributes #0 = { nounwind "disable-tail-calls"="true" } |
arsenm reviewed Oct 3, 2025
| ;CHECK: bne {{.*}} | ||
| ;CHECK-NEXT: nop | ||
| | ||
| %2 = call i32 @bar(i32 %a) |
Contributor
There was a problem hiding this comment.
Fix indent and use named values in tests
| // skip debug instruction | ||
| if (I->isDebugInstr()) | ||
| // Skip debug and generic instructions. | ||
| if (I->isDebugInstr() || (I->getOpcode() <= TargetOpcode::GENERIC_OP_END)) |
Contributor
There was a problem hiding this comment.
Generic is probably the wrong thing. isMetaInstruction?
Contributor Author
There was a problem hiding this comment.
This works, but I have a question:
Are debug instructions considered meta too? If so then I'll remove the redundant debug check too.
koachan changed the title arsenm reviewed Oct 3, 2025
Contributor
arsenm left a comment
arsenm left a comment There was a problem hiding this comment.
LGTM but meta check is redundant with debug
arsenm approved these changes Oct 3, 2025
MixedMatched pushed a commit to MixedMatched/llvm-project that referenced this pull request Oct 3, 2025
llvm#161111) Do not move meta instructions like `FAKE_USE`/`@llvm.fake.use` into delay slots, as they don't correspond to real machine instructions. This should fix crashes when compiling with, for example, `clang -Og`.
dyung pushed a commit to llvmbot/llvm-project that referenced this pull request Oct 6, 2025
llvm#161111) Do not move meta instructions like `FAKE_USE`/`@llvm.fake.use` into delay slots, as they don't correspond to real machine instructions. This should fix crashes when compiling with, for example, `clang -Og`. (cherry picked from commit 2e1fab9)
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit. This suggestion is invalid because no changes were made to the code. Suggestions cannot be applied while the pull request is closed. Suggestions cannot be applied while viewing a subset of changes. Only one suggestion per line can be applied in a batch. Add this suggestion to a batch that can be applied as a single commit. Applying suggestions on deleted lines is not supported. You must change the existing code in this line in order to create a valid suggestion. Outdated suggestions cannot be applied. This suggestion has been applied or marked resolved. Suggestions cannot be applied from pending reviews. Suggestions cannot be applied on multi-line comments. Suggestions cannot be applied while the pull request is queued to merge. Suggestion cannot be applied right now. Please check back later.
Do not move meta instructions like
FAKE_USE/@llvm.fake.useinto delay slots, as they don't correspond to real machine instructions.This should fix crashes when compiling with, for example,
clang -Og.