================
@@ -1200,16 +1200,61 @@ AAAMDWavesPerEU
&AAAMDWavesPerEU::createForPosition(const IRPosition &IRP,
llvm_unreachable("AAAMDWavesPerEU is only valid for function position");
}
-static bool inlineAsmUsesAGPRs(const InlineAsm *IA) {
- for (const auto &CI : IA->ParseConstraints()) {
+/// Compute the minimum number of AGPRs required to allocate the inline asm.
+static unsigned inlineAsmGetNumRequiredAGPRs(const InlineAsm *IA,
+ const CallBase &Call) {
+ unsigned ArgNo = 0;
+ unsigned ResNo = 0;
+ unsigned AGPRDefCount = 0;
+ unsigned AGPRUseCount = 0;
+ unsigned MaxPhysReg = 0;
+ const DataLayout &DL = Call.getFunction()->getParent()->getDataLayout();
+
+ for (const InlineAsm::ConstraintInfo &CI : IA->ParseConstraints()) {
+ Type *Ty = nullptr;
+ switch (CI.Type) {
+ case InlineAsm::isOutput: {
+ Ty = Call.getType();
+ if (auto *STy = dyn_cast<StructType>(Ty))
+ Ty = STy->getElementType(ResNo);
+ ++ResNo;
+ break;
+ }
+ case InlineAsm::isInput: {
+ Ty = Call.getArgOperand(ArgNo++)->getType();
+ break;
+ }
+ case InlineAsm::isLabel:
+ continue;
+ case InlineAsm::isClobber:
+ // Parse the physical register reference.
+ break;
+ }
+
for (StringRef Code : CI.Codes) {
- Code.consume_front("{");
- if (Code.starts_with("a"))
- return true;
+ if (Code.starts_with("a")) {
+ // Virtual register, compute number of registers based on the type.
+ //
+ // We ought to be going through TargetLowering to get the number of
+ // registers, but we should avoid the dependence on CodeGen here.
+ unsigned RegCount = divideCeil(DL.getTypeSizeInBits(Ty), 32);
+ if (CI.Type == InlineAsm::isOutput) {
+ AGPRDefCount += RegCount;
+ if (CI.isEarlyClobber)
+ AGPRUseCount += RegCount;
+ } else
+ AGPRUseCount += RegCount;
+ } else {
+ // Physical register reference
+ auto [Kind, RegIdx, NumRegs] = AMDGPU::parseAsmConstraintPhysReg(Code);
+ if (Kind == 'a')
+ MaxPhysReg = std::max(MaxPhysReg, std::min(RegIdx + NumRegs, 256u));
+ }
}
}
- return false;
+ unsigned MaxVirtReg = std::max(AGPRUseCount, AGPRDefCount);
+ return std::min(MaxVirtReg + MaxPhysReg, 256u);
----------------
ritter-x2a wrote:
For this code
```
define amdgpu_kernel void @foo() {
call void asm sideeffect "; use $0, $1, $2", "{a16},a,a"(i32 17, <8 x i32>
splat (i32 1), <16 x i32> splat (i32 2))
ret void
}
```
we allocate `; use a16, a[18:25], a[0:15]`, so the asm uses 25 AGPRs (arguably
26 since `a25` is used and `a17` is left out, not sure why it's not allocated
as `a[17:24]`, I'm not aware of alignment requirements for AGPRs).
This function computes 17 (the highest required physical register index + 1) +
24 (the number of virtual registers required) = 41 AGPRs required.
This over-approximation seems worth pointing out in a comment, if it's intended.
https://github.com/llvm/llvm-project/pull/150910
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