[X86] Return more accurate getNumSupportedRegs() (NFC) #71690
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llvm#70222 introduces a hook to return a more accurate number of registers supported for a specific subtarget (rather than target). However, while x86 registers were reordered to allow using this, the implementation still always returned NUM_TARGET_REGS. Adjust it to return a smaller number of registers depending on availability of avx/avx512/amx.
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@llvm/pr-subscribers-backend-x86 Author: Nikita Popov (nikic) Changes#70222 introduced a hook to return a more accurate number of registers supported for a specific subtarget (rather than target). However, while x86 registers were reordered to allow using this, the implementation currently still always returns NUM_TARGET_REGS. Adjust it to return a smaller number of registers depending on availability of avx/avx512/amx. The actual impact of this seems to be pretty small, on the order of 0.05% (http://llvm-compile-time-tracker.com/compare.php?from=d687057de8babc215d1cc883514085704ede5ab4&to=d218b6dece5d492e3a258524f4679b17c5d565d8&stat=instructions:u). Full diff: https://github.com/llvm/llvm-project/pull/71690.diff 1 Files Affected:
diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp
index 4fd8b6d17e862e0..b0bea42cafe11de 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.cpp
+++ b/llvm/lib/Target/X86/X86RegisterInfo.cpp
@@ -634,7 +634,15 @@ unsigned X86RegisterInfo::getNumSupportedRegs(const MachineFunction &MF) const {
(X86::K6_K7 + 1 == X86::TMMCFG) &&
(X86::TMM7 + 1 == X86::NUM_TARGET_REGS) &&
"Register number may be incorrect");
- return X86::NUM_TARGET_REGS;
+
+ const X86Subtarget &ST = MF.getSubtarget<X86Subtarget>();
+ if (ST.hasAMXTILE())
+ return X86::TMM7 + 1;
+ if (ST.hasAVX512())
+ return X86::K6_K7 + 1;
+ if (ST.hasAVX())
+ return X86::YMM15 + 1;
+ return X86::R15WH + 1;
}
bool X86RegisterInfo::isArgumentRegister(const MachineFunction &MF,
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LGTM, thanks @nikic! Ashamed not found this problem during review :(
#70222 introduced a hook to return a more accurate number of registers supported for a specific subtarget (rather than target). However, while x86 registers were reordered to allow using this, the implementation currently still always returns NUM_TARGET_REGS.
Adjust it to return a smaller number of registers depending on availability of avx/avx512/amx.
The actual impact of this seems to be pretty small, on the order of 0.05% (http://llvm-compile-time-tracker.com/compare.php?from=d687057de8babc215d1cc883514085704ede5ab4&to=d218b6dece5d492e3a258524f4679b17c5d565d8&stat=instructions:u).