[llvm] [AMDGPU] Rematerialize VGPR candidates when SGPR spills results in VGPR Excess (PR #168079)

[Lucas Ramirez via llvm-commits]

Juan Manuel Martinez =?utf-8?q?Caamaño?=,
Juan Manuel Martinez =?utf-8?q?Caamaño?=,
Juan Manuel Martinez =?utf-8?q?Caamaño?=,
Juan Manuel Martinez =?utf-8?q?Caamaño?=,
Juan Manuel Martinez =?utf-8?q?Caamaño?Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/168079 at github.com>


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@@ -97,6 +97,46 @@ void GCNRegPressure::inc(unsigned Reg,
   Value[RegKind] += Sign;
 }
 
+struct RegExcess {
+  unsigned SGPR = 0;
+  unsigned VGPR = 0;
+  unsigned ArchVGPR = 0;
+  unsigned AGPR = 0;
+
+  bool anyExcess() const { return SGPR || VGPR || ArchVGPR || AGPR; }
+  bool spillsToMemory() const { return VGPR || ArchVGPR || AGPR; }
+
+  RegExcess(const MachineFunction &MF, const GCNRegPressure &RP,
+            unsigned MaxSGPRs, unsigned MaxVGPRs) {
+    const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
+    SGPR = std::max(static_cast<int>(RP.getSGPRNum() - MaxSGPRs), 0);
+
+    // The number of virtual VGPRs required to handle excess SGPR
+    unsigned WaveSize = ST.getWavefrontSize();
+    unsigned VGPRForSGPRSpills = divideCeil(SGPR, WaveSize);
+
+    unsigned MaxArchVGPRs = ST.getAddressableNumArchVGPRs();
+
+    // Unified excess pressure conditions, accounting for VGPRs used for SGPR
+    // spills
+    VGPR = std::max(static_cast<int>(RP.getVGPRNum(ST.hasGFX90AInsts()) +
+                                     VGPRForSGPRSpills - MaxVGPRs),
+                    0);
+
+    // Arch VGPR excess pressure conditions, accounting for VGPRs used for SGPR
+    // spills
+    ArchVGPR = std::max(static_cast<int>(RP.getVGPRNum(false) +
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lucas-rami wrote:

Nevermind, tried this locally and it seems to work.

https://github.com/llvm/llvm-project/pull/168079