Fix cross-class spilling after rebase on main

Adapt accvgpr hazard check to use findPrecedingEmittingOp pattern
introduced on main, and update test CHECK lines for the new error
message format (emitError on Value loc, not program op).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Ivan Butygin <ivan.butygin@gmail.com>

Author: Hardcode84

waveasm/lib/Transforms/HazardMitigation.cpp

@@ -223,11 +223,10 @@ struct HazardMitigationPass
       // On GFX950 the VGPR destination of v_accvgpr_read_b32 is not
       // immediately available; a VALU that consumes it in the next cycle
       // reads stale data.  Insert s_nop 0 to cover the 1-cycle wait.
-      if (isAccVgprReadOp(current) && isVALUOp(next)) {
-        auto defs = getVGPRDefs(current);
-        auto uses = getVGPRUses(next);
-        if (hasIntersection(defs, uses))
-          insertionPoints.push_back(next);
+      if (isVALUOp(op) && i > 0) {
+        Operation *pred = findPrecedingEmittingOp(ops, i);
+        if (pred && isAccVgprReadOp(pred) && hasVGPRConflict(pred, op))
+          insertionPoints.push_back(op);
       }
     }
 

waveasm/lib/Transforms/LinearScanRegAlloc.cpp

@@ -330,29 +330,28 @@ LinearScanRegAlloc::allocate(ProgramOp program) {
   }
 
   // Step 5: Allocate VGPRs. On failure, evict to spare AGPRs.
-  if (failed(allocateRegClass(liveness.vregRanges, vgprPool, mapping, stats,
-                              tiedOperands, precoloredValues, "VGPR", program,
-                              maxVGPRs, liveness.maxVRegPressure,
-                              vgprStrategy.get(), &agprPool, &spills,
-                              &liveness)))
+  if (failed(allocateRegClass(
+          liveness.vregRanges, vgprPool, mapping, stats, tiedOperands,
+          precoloredValues, "VGPR", program, maxVGPRs, liveness.maxVRegPressure,
+          vgprStrategy.get(), &agprPool, &spills, &liveness)))
     return failure();
   stats.peakVGPRs = vgprPool.getPeakUsage();
 
   // Step 6: Allocate SGPRs (no cross-class spilling yet).
-  if (failed(allocateRegClass(
-          liveness.sregRanges, sgprPool, mapping, stats, tiedOperands,
-          precoloredValues, "SGPR", program, maxSGPRs, liveness.maxSRegPressure,
-          /*strategy=*/nullptr, /*altPool=*/nullptr, /*spills=*/nullptr,
-          &liveness)))
+  if (failed(allocateRegClass(liveness.sregRanges, sgprPool, mapping, stats,
+                              tiedOperands, precoloredValues, "SGPR", program,
+                              maxSGPRs, liveness.maxSRegPressure,
+                              /*strategy=*/nullptr, /*altPool=*/nullptr,
+                              /*spills=*/nullptr, &liveness)))
     return failure();
   stats.peakSGPRs = sgprPool.getPeakUsage();
 
   // Step 7: Allocate AGPRs (no cross-class spilling yet).
-  if (failed(allocateRegClass(
-          liveness.aregRanges, agprPool, mapping, stats, tiedOperands,
-          precoloredValues, "AGPR", program, maxAGPRs, liveness.maxARegPressure,
-          /*strategy=*/nullptr, /*altPool=*/nullptr, /*spills=*/nullptr,
-          &liveness)))
+  if (failed(allocateRegClass(liveness.aregRanges, agprPool, mapping, stats,
+                              tiedOperands, precoloredValues, "AGPR", program,
+                              maxAGPRs, liveness.maxARegPressure,
+                              /*strategy=*/nullptr, /*altPool=*/nullptr,
+                              /*spills=*/nullptr, &liveness)))
     return failure();
   stats.peakAGPRs = agprPool.getPeakUsage();
 

waveasm/test/Transforms/cross-class-spill-exhausted.mlir

@@ -3,7 +3,7 @@
 // Test: When both VGPR and AGPR pools are exhausted, allocation fails
 // with a diagnostic.  max-agprs=0 leaves no spare AGPRs for eviction.
 
-// CHECK: error: 'waveasm.program' op Failed to allocate VGPR
+// CHECK: error: Failed to allocate VGPR
 waveasm.program @both_exhausted target = #waveasm.target<#waveasm.gfx942, 5> abi = #waveasm.abi<> {
   %v0 = waveasm.precolored.vreg 0 : !waveasm.pvreg<0>
   %v1 = waveasm.precolored.vreg 1 : !waveasm.pvreg<1>

waveasm/test/Transforms/cross-class-spill-multi-reg.mlir

@@ -4,7 +4,7 @@
 // When the only live values are multi-register, eviction is not attempted
 // and allocation fails.
 
-// CHECK: error: 'waveasm.program' op Failed to allocate VGPR
+// CHECK: error: Failed to allocate VGPR
 waveasm.program @multi_reg_no_spill target = #waveasm.target<#waveasm.gfx942, 5> abi = #waveasm.abi<> {
   %srd = waveasm.precolored.sreg 0, 4 : !waveasm.psreg<0, 4>
   %voff = waveasm.precolored.vreg 0 : !waveasm.pvreg<0>

waveasm/test/Transforms/cross-class-spill-sgpr-unsupported.mlir

@@ -4,7 +4,7 @@
 // is not yet implemented.  The allocator does not attempt cross-class
 // eviction for SGPRs (altPool is nullptr).
 
-// CHECK: error: 'waveasm.program' op Failed to allocate SGPR
+// CHECK: error: Failed to allocate SGPR
 waveasm.program @sgpr_overflow target = #waveasm.target<#waveasm.gfx942, 5> abi = #waveasm.abi<> {
   %s0 = waveasm.precolored.sreg 0 : !waveasm.psreg<0>
   %s1 = waveasm.precolored.sreg 1 : !waveasm.psreg<1>