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| author | Preston Gurd <preston.gurd@intel.com> | 2013-01-04 20:54:54 +0000 |
|---|---|---|
| committer | Preston Gurd <preston.gurd@intel.com> | 2013-01-04 20:54:54 +0000 |
| commit | dd30b471750aca5c652873f9a8972df162b7e5eb (patch) | |
| tree | 9d8456fada6e2541f3a24cfe271493a526bd3a36 /lib/Target/X86/X86.h | |
| parent | 60507d53e7e8e6b0c537675f68204a93c3033de7 (diff) | |
The current Intel Atom microarchitecture has a feature whereby when a function
returns early then it is slightly faster to execute a sequence of NOP
instructions to wait until the return address is ready,
as opposed to simply stalling on the ret instruction
until the return address is ready.
When compiling for X86 Atom only, this patch will run a pass, called
"X86PadShortFunction" which will add NOP instructions where less than four
cycles elapse between function entry and return.
It includes tests.
Patch by Andy Zhang.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171524 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Target/X86/X86.h')
| -rw-r--r-- | lib/Target/X86/X86.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/lib/Target/X86/X86.h b/lib/Target/X86/X86.h index 1e7b98d94f..88dbb6d67a 100644 --- a/lib/Target/X86/X86.h +++ b/lib/Target/X86/X86.h @@ -63,6 +63,11 @@ FunctionPass *createX86JITCodeEmitterPass(X86TargetMachine &TM, /// FunctionPass *createEmitX86CodeToMemory(); +/// createX86PadShortFunctions - Return a pass that pads short functions +/// with NOOPs. This will prevent a stall when returning from the function +/// on the Atom. +FunctionPass *createX86PadShortFunctions(); + } // End llvm namespace #endif |