Reserve R9 on armv6 iOS before 3.0 #150835
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@llvm/pr-subscribers-backend-arm Author: None (Un1q32) ChangesThe iOS 2.x ABI had R9 as a reserved register, 3.0 made it available, but support for the 2.x ABI was never added to LLVM. We only use the 2.x ABI on armv6 since before 3.0 armv6 was the only architecture supported by iOS. Full diff: https://github.com/llvm/llvm-project/pull/150835.diff 1 Files Affected:
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.cpp b/llvm/lib/Target/ARM/ARMSubtarget.cpp
index 9f600e0c685ab..d6e226736ba66 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.cpp
+++ b/llvm/lib/Target/ARM/ARMSubtarget.cpp
@@ -227,7 +227,10 @@ void ARMSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
(Options.UnsafeFPMath || isTargetDarwin()))
HasNEONForFP = true;
- if (isRWPI())
+ if (isRWPI() ||
+ (isTargetIOS() &&
+ ARM::parseArch(TargetTriple.getArchName()) == ARM::ArchKind::ARMV6K &&
+ TargetTriple.isOSVersionLT(3, 0)))
ReserveR9 = true;
// If MVEVectorCostFactor is still 0 (has not been set to anything else), default it to 2
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jroelofs
reviewed
Aug 26, 2025
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Should probably be armv6 and armv6k actually. |
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All armv6 iOS devices were armv6k, and |
jroelofs
reviewed
Aug 27, 2025
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| ; RUN: llc <%s -mtriple=armv6k-apple-ios2 2>&1 | FileCheck %s -check-prefix=IOS2 | ||
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| ; RUN: llc <%s -mtriple=armv6k-apple-ios3 2>&1 | FileCheck %s -check-prefix=IOS3 | ||
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| ; RUN: llc <%s -mtriple=armv7-apple-ios2 2>&1 | FileCheck %s -check-prefix=IOSV7 | ||
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There was a problem hiding this comment.
style nit: RUN lines should be contiguous
Suggested change
| ; RUN: llc <%s -mtriple=armv6k-apple-ios2 2>&1 | FileCheck %s -check-prefix=IOS2 | |
| ; RUN: llc <%s -mtriple=armv6k-apple-ios3 2>&1 | FileCheck %s -check-prefix=IOS3 | |
| ; RUN: llc <%s -mtriple=armv7-apple-ios2 2>&1 | FileCheck %s -check-prefix=IOSV7 | |
| ; RUN: llc <%s -mtriple=armv6k-apple-ios2 2>&1 | FileCheck %s -check-prefix=IOS2 | |
| ; RUN: llc <%s -mtriple=armv6k-apple-ios3 2>&1 | FileCheck %s -check-prefix=IOS3 | |
| ; RUN: llc <%s -mtriple=armv7-apple-ios2 2>&1 | FileCheck %s -check-prefix=IOSV7 | |
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The iOS 2.x ABI had R9 as a reserved register, 3.0 made it available, but support for the 2.x ABI was never added to LLVM. We only use the 2.x ABI on armv6 since before 3.0 armv6 was the only architecture supported by iOS.