[llvm] [AMDGPU] Ignore inactive VGPRs in .vgpr_count (PR #144855)
Jay Foad via llvm-commits
llvm-commits at lists.llvm.org
Tue Jul 1 02:04:46 PDT 2025
================
@@ -139,268 +139,56 @@ AMDGPUResourceUsageAnalysis::analyzeResourceUsage(
Info.UsesVCC =
MRI.isPhysRegUsed(AMDGPU::VCC_LO) || MRI.isPhysRegUsed(AMDGPU::VCC_HI);
+ Info.NumExplicitSGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::SGPR_32RegClass,
+ /*IncludeCalls=*/false);
+ if (ST.hasMAIInsts())
+ Info.NumAGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::AGPR_32RegClass,
+ /*IncludeCalls=*/false);
- // If there are no calls, MachineRegisterInfo can tell us the used register
- // count easily.
// A tail call isn't considered a call for MachineFrameInfo's purposes.
- if (!FrameInfo.hasCalls() && !FrameInfo.hasTailCall()) {
- Info.NumVGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::VGPR_32RegClass);
- Info.NumExplicitSGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::SGPR_32RegClass);
- if (ST.hasMAIInsts())
- Info.NumAGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::AGPR_32RegClass);
+ bool HasCalls = FrameInfo.hasCalls() || FrameInfo.hasTailCall();
+ // Functions that use the llvm.amdgcn.init.whole.wave intrinsic often have
+ // VGPR arguments that are only added for the purpose of preserving the
+ // inactive lanes. These should not be included in the number of used VGPRs.
+ bool NeedsExplicitVGPRCount = MFI->hasInitWholeWave();
+ if (!HasCalls && !NeedsExplicitVGPRCount) {
+
+ Info.NumVGPR = TRI.getNumUsedPhysRegs(MRI, AMDGPU::VGPR_32RegClass,
+ /*IncludeCalls=*/false);
return Info;
}
int32_t MaxVGPR = -1;
- int32_t MaxAGPR = -1;
- int32_t MaxSGPR = -1;
Info.CalleeSegmentSize = 0;
for (const MachineBasicBlock &MBB : MF) {
for (const MachineInstr &MI : MBB) {
- // TODO: Check regmasks? Do they occur anywhere except calls?
- for (const MachineOperand &MO : MI.operands()) {
- unsigned Width = 0;
- bool IsSGPR = false;
- bool IsAGPR = false;
-
- if (!MO.isReg())
- continue;
-
- Register Reg = MO.getReg();
- switch (Reg) {
- case AMDGPU::EXEC:
- case AMDGPU::EXEC_LO:
- case AMDGPU::EXEC_HI:
- case AMDGPU::SCC:
- case AMDGPU::M0:
- case AMDGPU::M0_LO16:
- case AMDGPU::M0_HI16:
- case AMDGPU::SRC_SHARED_BASE_LO:
- case AMDGPU::SRC_SHARED_BASE:
- case AMDGPU::SRC_SHARED_LIMIT_LO:
- case AMDGPU::SRC_SHARED_LIMIT:
- case AMDGPU::SRC_PRIVATE_BASE_LO:
- case AMDGPU::SRC_PRIVATE_BASE:
- case AMDGPU::SRC_PRIVATE_LIMIT_LO:
- case AMDGPU::SRC_PRIVATE_LIMIT:
- case AMDGPU::SRC_POPS_EXITING_WAVE_ID:
- case AMDGPU::SGPR_NULL:
- case AMDGPU::SGPR_NULL64:
- case AMDGPU::MODE:
- continue;
-
- case AMDGPU::NoRegister:
- assert(MI.isDebugInstr() &&
- "Instruction uses invalid noreg register");
- continue;
-
- case AMDGPU::VCC:
- case AMDGPU::VCC_LO:
- case AMDGPU::VCC_HI:
- case AMDGPU::VCC_LO_LO16:
- case AMDGPU::VCC_LO_HI16:
- case AMDGPU::VCC_HI_LO16:
- case AMDGPU::VCC_HI_HI16:
- Info.UsesVCC = true;
- continue;
-
- case AMDGPU::FLAT_SCR:
- case AMDGPU::FLAT_SCR_LO:
- case AMDGPU::FLAT_SCR_HI:
- continue;
-
- case AMDGPU::XNACK_MASK:
- case AMDGPU::XNACK_MASK_LO:
- case AMDGPU::XNACK_MASK_HI:
- llvm_unreachable("xnack_mask registers should not be used");
-
- case AMDGPU::LDS_DIRECT:
- llvm_unreachable("lds_direct register should not be used");
-
- case AMDGPU::TBA:
- case AMDGPU::TBA_LO:
- case AMDGPU::TBA_HI:
- case AMDGPU::TMA:
- case AMDGPU::TMA_LO:
- case AMDGPU::TMA_HI:
- llvm_unreachable("trap handler registers should not be used");
-
- case AMDGPU::SRC_VCCZ:
- llvm_unreachable("src_vccz register should not be used");
-
- case AMDGPU::SRC_EXECZ:
- llvm_unreachable("src_execz register should not be used");
-
- case AMDGPU::SRC_SCC:
- llvm_unreachable("src_scc register should not be used");
-
- default:
- break;
- }
-
- if (AMDGPU::SGPR_32RegClass.contains(Reg) ||
- AMDGPU::SGPR_LO16RegClass.contains(Reg) ||
- AMDGPU::SGPR_HI16RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 1;
- } else if (AMDGPU::VGPR_32RegClass.contains(Reg) ||
- AMDGPU::VGPR_16RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 1;
- } else if (AMDGPU::AGPR_32RegClass.contains(Reg) ||
- AMDGPU::AGPR_LO16RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 1;
- } else if (AMDGPU::SGPR_64RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 2;
- } else if (AMDGPU::VReg_64RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 2;
- } else if (AMDGPU::AReg_64RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 2;
- } else if (AMDGPU::VReg_96RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 3;
- } else if (AMDGPU::SReg_96RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 3;
- } else if (AMDGPU::AReg_96RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 3;
- } else if (AMDGPU::SGPR_128RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 4;
- } else if (AMDGPU::VReg_128RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 4;
- } else if (AMDGPU::AReg_128RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 4;
- } else if (AMDGPU::VReg_160RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 5;
- } else if (AMDGPU::SReg_160RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 5;
- } else if (AMDGPU::AReg_160RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 5;
- } else if (AMDGPU::VReg_192RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 6;
- } else if (AMDGPU::SReg_192RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 6;
- } else if (AMDGPU::AReg_192RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 6;
- } else if (AMDGPU::VReg_224RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 7;
- } else if (AMDGPU::SReg_224RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 7;
- } else if (AMDGPU::AReg_224RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 7;
- } else if (AMDGPU::SReg_256RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 8;
- } else if (AMDGPU::VReg_256RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 8;
- } else if (AMDGPU::AReg_256RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 8;
- } else if (AMDGPU::VReg_288RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 9;
- } else if (AMDGPU::SReg_288RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 9;
- } else if (AMDGPU::AReg_288RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 9;
- } else if (AMDGPU::VReg_320RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 10;
- } else if (AMDGPU::SReg_320RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 10;
- } else if (AMDGPU::AReg_320RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 10;
- } else if (AMDGPU::VReg_352RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 11;
- } else if (AMDGPU::SReg_352RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 11;
- } else if (AMDGPU::AReg_352RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 11;
- } else if (AMDGPU::VReg_384RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 12;
- } else if (AMDGPU::SReg_384RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 12;
- } else if (AMDGPU::AReg_384RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 12;
- } else if (AMDGPU::SReg_512RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 16;
- } else if (AMDGPU::VReg_512RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 16;
- } else if (AMDGPU::AReg_512RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 16;
- } else if (AMDGPU::SReg_1024RegClass.contains(Reg)) {
- IsSGPR = true;
- Width = 32;
- } else if (AMDGPU::VReg_1024RegClass.contains(Reg)) {
- IsSGPR = false;
- Width = 32;
- } else if (AMDGPU::AReg_1024RegClass.contains(Reg)) {
- IsSGPR = false;
- IsAGPR = true;
- Width = 32;
- } else {
- // We only expect TTMP registers or registers that do not belong to
- // any RC.
- assert((AMDGPU::TTMP_32RegClass.contains(Reg) ||
- AMDGPU::TTMP_64RegClass.contains(Reg) ||
- AMDGPU::TTMP_128RegClass.contains(Reg) ||
- AMDGPU::TTMP_256RegClass.contains(Reg) ||
- AMDGPU::TTMP_512RegClass.contains(Reg) ||
- !TRI.getPhysRegBaseClass(Reg)) &&
- "Unknown register class");
- }
- unsigned HWReg = TRI.getHWRegIndex(Reg);
- int MaxUsed = HWReg + Width - 1;
- if (IsSGPR) {
- MaxSGPR = MaxUsed > MaxSGPR ? MaxUsed : MaxSGPR;
- } else if (IsAGPR) {
- MaxAGPR = MaxUsed > MaxAGPR ? MaxUsed : MaxAGPR;
- } else {
+ if (NeedsExplicitVGPRCount) {
+ for (unsigned i = 0; i < MI.getNumOperands(); ++i) {
+ const MachineOperand &MO = MI.getOperand(i);
+
+ if (!MO.isReg())
+ continue;
+ Register Reg = MO.getReg();
+ const TargetRegisterClass *RC = TRI.getPhysRegBaseClass(Reg);
+
+ if (!RC || !TRI.isVGPRClass(RC))
+ continue;
+
+ // Skip inactive VGPRs in chain functions with the init.whole.wave
+ // intrinsic. These will only appear as implicit use operands on the
+ // chain call, and as the def of an IMPLICIT_DEF. We're going to skip
+ // implicit defs unconditionally though because if they're important
+ // in a different context then they will be counted when they are
+ // used.
+ bool IsChainCall =
+ MFI->isChainFunction() && MI.getOpcode() == AMDGPU::SI_TCRETURN;
+ if (IsChainCall || MI.isImplicitDef())
+ continue;
+
+ unsigned Width = TRI.getRegSizeInBits(*RC) / 32;
----------------
jayfoad wrote:
You probably need `divideCeil` to prevent 16/32 from rounding down to 0.
https://github.com/llvm/llvm-project/pull/144855
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