Issue Description:

https://ci.swift.org/job/swift-master-source-compat-suite/4248

05:03:45 PASS: Starscream, 4.0, 114e5d, Starscream, generic/platform=iOS
05:03:45 $ git -C /Users/buildnode/jenkins/workspace-private/swift-master-source-compat-suite/project_cache/Starscream/examples/SimpleTest rev-parse --show-toplevel
05:03:59 PASS: Starscream, 4.0, 114e5d, Starscream, generic/platform=iOS
05:03:59 $ git -C /Users/buildnode/jenkins/workspace-private/swift-master-source-compat-suite/project_cache/Starscream rev-parse --show-toplevel
05:04:13 PASS: Starscream, 4.0, 114e5d, Starscream, generic/platform=iOS
05:04:13 $ git -C /Users/buildnode/jenkins/workspace-private/swift-master-source-compat-suite/project_cache/Starscream/examples/AutobahnTest rev-parse --show-toplevel
05:04:27 FAIL: Starscream, 5.1, a2ed45, Starscream, generic/platform=iOS
05:04:27 $ git -C /Users/buildnode/jenkins/workspace-private/swift-master-source-compat-suite/project_cache/Starscream/examples/SimpleTest rev-parse --show-toplevel
05:04:41 FAIL: Starscream, 5.1, a2ed45, Starscream, generic/platform=iOS
05:04:41 $ git -C /Users/buildnode/jenkins/workspace-private/swift-master-source-compat-suite/project_cache/Starscream rev-parse --show-toplevel
05:04:55 FAIL: Starscream, 5.1, a2ed45, Starscream, generic/platform=iOS
05:04:56 $ git -C /Users/buildnode/jenkins/workspace-private/swift-master-source-compat-suite/project_cache/Surge rev-parse --show-toplevel

Assertion failed: (getMaxFPOffset(MF.getFunction(), *AFI) <= FPOffset && "Max FP estimation is wrong"), function emitPrologue, file /Users/buildnode/jenkins/workspace-private/swift-master-source-compat-suite/llvm/lib/Target/ARM/ARMFrameLowering.cpp, line 464.
Stack dump:
0. Running pass 'Function Pass Manager' on module '/Users/buildnode/jenkins/workspace-private/swift-master-source-compat-suite/project_cache/Starscream/build/Build/Intermediates.noindex/Starscream.build/Release-iphoneos/Starscream.build/Objects-normal/armv7/Compression.o'.

1. Running pass 'Prologue/Epilogue Insertion & Frame Finalization' on function '@"$s10Starscream9WebSocketCMr"'
   0 swift 0x00000001048324f5 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 37
   1 swift 0x00000001048314f8 llvm::sys::RunSignalHandlers() + 248
   2 swift 0x0000000104832ae8 SignalHandler(int) + 264
   3 libsystem_platform.dylib 0x00007fff6e9a2b5d _sigtramp + 29
   4 libsystem_platform.dylib 0x00007fd011590520 _sigtramp + 2730416608
   5 libsystem_c.dylib 0x00007fff6e85c6a6 abort + 127
   6 libsystem_c.dylib 0x00007fff6e82520d basename_r + 0
   7 swift 0x0000000104d79cd3 llvm::ARMFrameLowering::emitPrologue(llvm::MachineFunction&, llvm::MachineBasicBlock&) const (.cold.2) + 35
   8 swift 0x0000000101b64188 llvm::ARMFrameLowering::emitPrologue(llvm::MachineFunction&, llvm::MachineBasicBlock&) const + 10424