[SPARC] Prevent meta instructions from being inserted into delay slots #161111
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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`.
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@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" }
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arsenm
reviewed
Oct 3, 2025
| ;CHECK: bne {{.*}} | ||
| ;CHECK-NEXT: nop | ||
|
|
||
| %2 = call i32 @bar(i32 %a) |
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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)) |
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Generic is probably the wrong thing. isMetaInstruction?
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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
arsenm
approved these changes
Oct 3, 2025
MixedMatched
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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
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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)
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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.