AMDGPU: Fix crash in rewrite AGPR copy MFMA pass on dead valnos #153915

arsenm · 2025-08-16T02:39:39Z

Test isn't great, probably won't reliably reproduce the problem
in the future.

Test isn't great, probably won't reliably reproduce the problem in the future.

arsenm · 2025-08-16T02:39:55Z

AMDGPU: Fix crash in rewrite AGPR copy MFMA pass on dead valnos #153915 👈 (View in Graphite)
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llvmbot · 2025-08-16T02:40:10Z

@llvm/pr-subscribers-backend-amdgpu

Author: Matt Arsenault (arsenm)

Changes

Test isn't great, probably won't reliably reproduce the problem
in the future.

Full diff: https://github.com/llvm/llvm-project/pull/153915.diff

2 Files Affected:

(modified) llvm/lib/Target/AMDGPU/AMDGPURewriteAGPRCopyMFMA.cpp (+3)
(added) llvm/test/CodeGen/AMDGPU/av-split-dead-valno-crash.ll (+211)

diff --git a/llvm/lib/Target/AMDGPU/AMDGPURewriteAGPRCopyMFMA.cpp b/llvm/lib/Target/AMDGPU/AMDGPURewriteAGPRCopyMFMA.cpp
index bab83483f3de1..20b5fd94aba94 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPURewriteAGPRCopyMFMA.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPURewriteAGPRCopyMFMA.cpp
@@ -147,6 +147,9 @@ bool AMDGPURewriteAGPRCopyMFMAImpl::run(MachineFunction &MF) const {
 
     // TODO: Test multiple uses
     for (VNInfo *VNI : LI.vnis()) {
+      if (VNI->isPHIDef() || VNI->isUnused())
+        continue;
+
       MachineInstr *DefMI = LIS.getInstructionFromIndex(VNI->def);
 
       // TODO: Handle SplitKit produced copy bundles for partially defined
diff --git a/llvm/test/CodeGen/AMDGPU/av-split-dead-valno-crash.ll b/llvm/test/CodeGen/AMDGPU/av-split-dead-valno-crash.ll
new file mode 100644
index 0000000000000..89fe0ab526a8a
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/av-split-dead-valno-crash.ll
@@ -0,0 +1,211 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx942 -stress-regalloc=18 < %s | FileCheck %s
+
+define amdgpu_kernel void @vgpr_mfma_pass_av_split_crash(double %arg1, i1 %arg2, i1 %cond.i.i.i2295, ptr addrspace(1) %ptr, ptr %ptr1) #0 {
+; CHECK-LABEL: vgpr_mfma_pass_av_split_crash:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    s_load_dword s0, s[4:5], 0x8
+; CHECK-NEXT:    s_load_dwordx2 s[10:11], s[4:5], 0x0
+; CHECK-NEXT:    s_load_dwordx4 s[12:15], s[4:5], 0x10
+; CHECK-NEXT:    v_mov_b32_e32 v1, 0x3e21eeb6
+; CHECK-NEXT:    v_mov_b32_e32 v2, 0xa17f65f6
+; CHECK-NEXT:    s_waitcnt lgkmcnt(0)
+; CHECK-NEXT:    s_bitcmp1_b32 s0, 0
+; CHECK-NEXT:    s_cselect_b64 s[16:17], -1, 0
+; CHECK-NEXT:    s_xor_b64 s[18:19], s[16:17], -1
+; CHECK-NEXT:    s_bitcmp1_b32 s0, 8
+; CHECK-NEXT:    s_cselect_b64 s[2:3], -1, 0
+; CHECK-NEXT:    v_cndmask_b32_e64 v0, 0, 1, s[2:3]
+; CHECK-NEXT:    s_xor_b64 s[20:21], s[2:3], -1
+; CHECK-NEXT:    v_cmp_ne_u32_e64 s[0:1], 1, v0
+; CHECK-NEXT:    s_and_b64 s[2:3], exec, s[2:3]
+; CHECK-NEXT:    v_mov_b32_e32 v0, 0x9037ab78
+; CHECK-NEXT:    v_mov_b32_e32 v3, 0xbe927e4f
+; CHECK-NEXT:    v_mov_b32_e32 v4, 0x19f4ec90
+; CHECK-NEXT:    v_mov_b32_e32 v5, 0x3efa01a0
+; CHECK-NEXT:    v_mov_b32_e32 v6, 0x16c16967
+; CHECK-NEXT:    v_mov_b32_e32 v7, 0xbf56c16c
+; CHECK-NEXT:    v_mov_b32_e32 v8, 0x69efb384
+; CHECK-NEXT:    v_mov_b32_e32 v9, 0x3f4b2bb0
+; CHECK-NEXT:    v_mov_b32_e32 v10, 0xa57d9582
+; CHECK-NEXT:    v_mov_b32_e32 v11, 0xbf8c6ea4
+; CHECK-NEXT:    v_mov_b32_e32 v12, 0xe82d3ff0
+; CHECK-NEXT:    v_mov_b32_e32 v13, 0xbfa59976
+; CHECK-NEXT:    v_mov_b32_e32 v14, 0x8427b883
+; CHECK-NEXT:    v_mov_b32_e32 v15, 0x3fae1bb4
+; CHECK-NEXT:    s_mov_b64 s[22:23], 0
+; CHECK-NEXT:    v_mov_b32_e32 v16, 0x57b87036
+; CHECK-NEXT:    v_mov_b32_e32 v17, 0x3fb3b136
+; CHECK-NEXT:    s_and_b64 s[4:5], exec, s[16:17]
+; CHECK-NEXT:    v_mov_b32_e32 v18, 0x55555523
+; CHECK-NEXT:    v_mov_b32_e32 v19, 0xbfd55555
+; CHECK-NEXT:    s_and_b64 s[6:7], exec, s[18:19]
+; CHECK-NEXT:    v_mov_b32_e32 v20, 0
+; CHECK-NEXT:    ; implicit-def: $agpr0_agpr1
+; CHECK-NEXT:    ; implicit-def: $vgpr22_vgpr23
+; CHECK-NEXT:    s_branch .LBB0_2
+; CHECK-NEXT:  .LBB0_1: ; %Flow9
+; CHECK-NEXT:    ; in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT:    s_andn2_b64 vcc, exec, s[24:25]
+; CHECK-NEXT:    s_cbranch_vccz .LBB0_17
+; CHECK-NEXT:  .LBB0_2: ; %._crit_edge1942.i.i.i3548
+; CHECK-NEXT:    ; =>This Loop Header: Depth=1
+; CHECK-NEXT:    ; Child Loop BB0_6 Depth 2
+; CHECK-NEXT:    s_and_b64 vcc, exec, s[0:1]
+; CHECK-NEXT:    s_cbranch_vccnz .LBB0_9
+; CHECK-NEXT:  ; %bb.3: ; %.preheader1868.i.i.i3244
+; CHECK-NEXT:    ; in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT:    s_mov_b64 vcc, s[4:5]
+; CHECK-NEXT:    s_cbranch_vccz .LBB0_10
+; CHECK-NEXT:  ; %bb.4: ; %.preheader1855.i.i.i3329.preheader
+; CHECK-NEXT:    ; in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT:    v_mov_b64_e32 v[24:25], s[14:15]
+; CHECK-NEXT:    flat_load_dwordx2 v[24:25], v[24:25]
+; CHECK-NEXT:    v_mov_b64_e32 v[26:27], v[0:1]
+; CHECK-NEXT:    v_mov_b64_e32 v[28:29], v[2:3]
+; CHECK-NEXT:    v_mov_b64_e32 v[30:31], v[16:17]
+; CHECK-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
+; CHECK-NEXT:    v_fmac_f64_e32 v[26:27], 0, v[24:25]
+; CHECK-NEXT:    v_fmac_f64_e32 v[28:29], 0, v[26:27]
+; CHECK-NEXT:    v_mov_b64_e32 v[26:27], v[4:5]
+; CHECK-NEXT:    v_fmac_f64_e32 v[26:27], 0, v[28:29]
+; CHECK-NEXT:    v_mov_b64_e32 v[28:29], v[6:7]
+; CHECK-NEXT:    v_fmac_f64_e32 v[28:29], 0, v[26:27]
+; CHECK-NEXT:    v_mov_b64_e32 v[26:27], v[8:9]
+; CHECK-NEXT:    v_fmac_f64_e32 v[26:27], 0, v[28:29]
+; CHECK-NEXT:    v_mov_b64_e32 v[28:29], v[10:11]
+; CHECK-NEXT:    v_fmac_f64_e32 v[28:29], 0, v[26:27]
+; CHECK-NEXT:    v_mov_b64_e32 v[26:27], v[12:13]
+; CHECK-NEXT:    v_fmac_f64_e32 v[26:27], 0, v[28:29]
+; CHECK-NEXT:    v_mov_b64_e32 v[28:29], v[14:15]
+; CHECK-NEXT:    v_fmac_f64_e32 v[28:29], 0, v[26:27]
+; CHECK-NEXT:    v_fmac_f64_e32 v[30:31], 0, v[28:29]
+; CHECK-NEXT:    v_mov_b64_e32 v[26:27], v[18:19]
+; CHECK-NEXT:    v_fmac_f64_e32 v[26:27], 0, v[30:31]
+; CHECK-NEXT:    v_mov_b64_e32 v[30:31], 0
+; CHECK-NEXT:    s_branch .LBB0_6
+; CHECK-NEXT:  .LBB0_5: ; %Flow
+; CHECK-NEXT:    ; in Loop: Header=BB0_6 Depth=2
+; CHECK-NEXT:    s_and_b64 vcc, exec, s[8:9]
+; CHECK-NEXT:    s_cbranch_vccnz .LBB0_11
+; CHECK-NEXT:  .LBB0_6: ; %.preheader1855.i.i.i3329
+; CHECK-NEXT:    ; Parent Loop BB0_2 Depth=1
+; CHECK-NEXT:    ; => This Inner Loop Header: Depth=2
+; CHECK-NEXT:    v_mov_b64_e32 v[28:29], v[30:31]
+; CHECK-NEXT:    s_mov_b64 s[24:25], -1
+; CHECK-NEXT:    s_mov_b64 s[8:9], -1
+; CHECK-NEXT:    s_mov_b64 vcc, s[2:3]
+; CHECK-NEXT:    ; implicit-def: $vgpr30_vgpr31
+; CHECK-NEXT:    s_cbranch_vccz .LBB0_5
+; CHECK-NEXT:  ; %bb.7: ; %.lr.ph2070.i.i.i3291
+; CHECK-NEXT:    ; in Loop: Header=BB0_6 Depth=2
+; CHECK-NEXT:    v_accvgpr_read_b32 v31, a1
+; CHECK-NEXT:    v_accvgpr_read_b32 v30, a0
+; CHECK-NEXT:    s_mov_b64 s[8:9], s[18:19]
+; CHECK-NEXT:    s_mov_b64 vcc, s[6:7]
+; CHECK-NEXT:    s_cbranch_vccz .LBB0_5
+; CHECK-NEXT:  ; %bb.8: ; %.preheader1856.preheader.i.i.i3325
+; CHECK-NEXT:    ; in Loop: Header=BB0_6 Depth=2
+; CHECK-NEXT:    s_mov_b64 s[24:25], 0
+; CHECK-NEXT:    v_mov_b64_e32 v[30:31], v[26:27]
+; CHECK-NEXT:    s_mov_b64 s[8:9], 0
+; CHECK-NEXT:    s_branch .LBB0_5
+; CHECK-NEXT:  .LBB0_9: ; in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT:    v_mov_b64_e32 v[24:25], s[10:11]
+; CHECK-NEXT:    v_accvgpr_write_b32 a0, v24
+; CHECK-NEXT:    s_mov_b64 s[22:23], 0
+; CHECK-NEXT:    v_accvgpr_write_b32 a1, v25
+; CHECK-NEXT:    s_mov_b64 s[8:9], s[20:21]
+; CHECK-NEXT:    s_branch .LBB0_15
+; CHECK-NEXT:  .LBB0_10: ; in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT:    s_mov_b64 s[8:9], -1
+; CHECK-NEXT:    v_mov_b64_e32 v[22:23], 0
+; CHECK-NEXT:    s_branch .LBB0_15
+; CHECK-NEXT:  .LBB0_11: ; %loop.exit.guard
+; CHECK-NEXT:    ; in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT:    s_and_b64 vcc, exec, s[24:25]
+; CHECK-NEXT:    s_cbranch_vccz .LBB0_13
+; CHECK-NEXT:  ; %bb.12: ; %._crit_edge2105.i.i.i2330.loopexit
+; CHECK-NEXT:    ; in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT:    v_cmp_nlg_f64_e64 s[8:9], 0, v[28:29]
+; CHECK-NEXT:    v_accvgpr_write_b32 a0, v24
+; CHECK-NEXT:    v_cndmask_b32_e64 v23, v23, 0, s[16:17]
+; CHECK-NEXT:    v_cndmask_b32_e64 v26, 0, 1, s[8:9]
+; CHECK-NEXT:    v_mov_b32_e32 v27, v26
+; CHECK-NEXT:    s_and_b64 s[8:9], exec, s[16:17]
+; CHECK-NEXT:    v_cndmask_b32_e64 v22, v22, 0, s[16:17]
+; CHECK-NEXT:    global_store_dwordx2 v20, v[26:27], s[12:13]
+; CHECK-NEXT:    s_cselect_b32 s23, s23, 0
+; CHECK-NEXT:    s_cselect_b32 s22, s22, 0
+; CHECK-NEXT:    s_mov_b64 s[8:9], -1
+; CHECK-NEXT:    s_branch .LBB0_14
+; CHECK-NEXT:  .LBB0_13: ; in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT:    v_accvgpr_write_b32 a0, v24
+; CHECK-NEXT:    s_mov_b64 s[8:9], 0
+; CHECK-NEXT:    v_mov_b64_e32 v[22:23], 0
+; CHECK-NEXT:  .LBB0_14: ; %Flow6
+; CHECK-NEXT:    ; in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT:    v_accvgpr_write_b32 a1, v25
+; CHECK-NEXT:  .LBB0_15: ; %Flow6
+; CHECK-NEXT:    ; in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT:    s_mov_b64 s[24:25], -1
+; CHECK-NEXT:    s_and_b64 vcc, exec, s[8:9]
+; CHECK-NEXT:    s_cbranch_vccz .LBB0_1
+; CHECK-NEXT:  ; %bb.16: ; %._crit_edge2105.i.i.i2330
+; CHECK-NEXT:    ; in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT:    v_mov_b32_e32 v21, v20
+; CHECK-NEXT:    s_mov_b64 s[24:25], 0
+; CHECK-NEXT:    global_store_dwordx2 v20, v[20:21], s[12:13]
+; CHECK-NEXT:    s_branch .LBB0_1
+; CHECK-NEXT:  .LBB0_17: ; %DummyReturnBlock
+; CHECK-NEXT:    s_endpgm
+entry:
+  br label %._crit_edge1942.i.i.i3548
+
+._crit_edge1942.i.i.i3548:                        ; preds = %._crit_edge2105.i.i.i2330, %entry
+  %.sroa.02591.0.i.i.i226323 = phi double [ poison, %entry ], [ %.sroa.02591.3.i.i.i2301, %._crit_edge2105.i.i.i2330 ]
+  %.sroa.3.0.i.i.i2270 = phi double [ poison, %entry ], [ %.sroa.3.3.i.i.i2308, %._crit_edge2105.i.i.i2330 ]
+  %.014942244.i.i.i2280 = phi double [ 0.000000e+00, %entry ], [ %.31497.i.i.i2317, %._crit_edge2105.i.i.i2330 ]
+  br i1 %cond.i.i.i2295, label %.preheader1868.i.i.i3244, label %._crit_edge2105.i.i.i2330
+
+.preheader1868.i.i.i3244:                         ; preds = %._crit_edge1942.i.i.i3548
+  %i = load double, ptr %ptr1, align 8
+  %i3 = call double @llvm.fma.f64(double %i, double 0.000000e+00, double 0x3E21EEB69037AB78)
+  %i4 = call double @llvm.fma.f64(double 0.000000e+00, double %i3, double 0xBE927E4FA17F65F6)
+  %i5 = call double @llvm.fma.f64(double 0.000000e+00, double %i4, double 0x3EFA01A019F4EC90)
+  %i6 = call double @llvm.fma.f64(double 0.000000e+00, double %i5, double 0xBF56C16C16C16967)
+  %spec.select.i.i.i3288 = select i1 %arg2, double 0.000000e+00, double %.sroa.3.0.i.i.i2270
+  br i1 %arg2, label %.preheader1855.i.i.i3329, label %._crit_edge2105.i.i.i2330
+
+.lr.ph2070.i.i.i3291:                             ; preds = %.preheader1855.i.i.i3329
+  br i1 %arg2, label %.preheader1855.i.i.i3329, label %.preheader1856.preheader.i.i.i3325
+
+.preheader1856.preheader.i.i.i3325:               ; preds = %.lr.ph2070.i.i.i3291
+  %i11 = call double @llvm.fma.f64(double 0.000000e+00, double %i6, double 0x3F4B2BB069EFB384)
+  %i14 = call double @llvm.fma.f64(double 0.000000e+00, double %i11, double 0xBF8C6EA4A57D9582)
+  %i18 = call double @llvm.fma.f64(double 0.000000e+00, double %i14, double 0xBFA59976E82D3FF0)
+  %i21 = call double @llvm.fma.f64(double 0.000000e+00, double %i18, double 0x3FAE1BB48427B883)
+  %i23 = call double @llvm.fma.f64(double 0.000000e+00, double %i21, double 0x3FB3B13657B87036)
+  %i28 = call double @llvm.fma.f64(double 0.000000e+00, double %i23, double 0xBFD5555555555523)
+  br label %.preheader1855.i.i.i3329
+
+.preheader1855.i.i.i3329:                         ; preds = %.preheader1856.preheader.i.i.i3325, %.lr.ph2070.i.i.i3291, %.preheader1868.i.i.i3244
+  %.sroa.02591.4.i.i.i3335 = phi double [ %i28, %.preheader1856.preheader.i.i.i3325 ], [ %.sroa.02591.0.i.i.i226323, %.lr.ph2070.i.i.i3291 ], [ 0.000000e+00, %.preheader1868.i.i.i3244 ]
+  %.21496.ph.i.i.i3348 = select i1 %arg2, double %.014942244.i.i.i2280, double 0.000000e+00
+  %i31 = fcmp one double %.sroa.02591.4.i.i.i3335, 0.000000e+00
+  %i32 = select i1 %i31, <2 x i32> zeroinitializer, <2 x i32> splat (i32 1)
+  store <2 x i32> %i32, ptr addrspace(1) %ptr, align 8
+  br i1 %cond.i.i.i2295, label %.lr.ph2070.i.i.i3291, label %._crit_edge2105.i.i.i2330
+
+._crit_edge2105.i.i.i2330:                        ; preds = %.preheader1855.i.i.i3329, %.preheader1868.i.i.i3244, %._crit_edge1942.i.i.i3548
+  %.sroa.02591.3.i.i.i2301 = phi double [ %.sroa.02591.0.i.i.i226323, %.preheader1868.i.i.i3244 ], [ %arg1, %._crit_edge1942.i.i.i3548 ], [ %i, %.preheader1855.i.i.i3329 ]
+  %.sroa.3.3.i.i.i2308 = phi double [ 0.000000e+00, %.preheader1868.i.i.i3244 ], [ %.sroa.3.0.i.i.i2270, %._crit_edge1942.i.i.i3548 ], [ %spec.select.i.i.i3288, %.preheader1855.i.i.i3329 ]
+  %.31497.i.i.i2317 = phi double [ %.014942244.i.i.i2280, %.preheader1868.i.i.i3244 ], [ 0.000000e+00, %._crit_edge1942.i.i.i3548 ], [ %.21496.ph.i.i.i3348, %.preheader1855.i.i.i3329 ]
+  store double 0.000000e+00, ptr addrspace(1) %ptr, align 8
+  br label %._crit_edge1942.i.i.i3548
+}
+
+declare double @llvm.fma.f64(double, double, double) #1
+
+attributes #0 = { "amdgpu-waves-per-eu"="8,8" "target-cpu"="gfx942" }
+attributes #1 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }

AMDGPU: Fix crash in rewrite AGPR copy MFMA pass on dead valnos

2526814

Test isn't great, probably won't reliably reproduce the problem in the future.

arsenm added the backend:AMDGPU label Aug 16, 2025 — with Graphite App

arsenm requested review from jayfoad, lucas-rami, perlfu and ronlieb August 16, 2025 02:40

arsenm marked this pull request as ready for review August 16, 2025 02:40

ronlieb approved these changes Aug 16, 2025

View reviewed changes

arsenm merged commit 30007a5 into main Aug 16, 2025
13 checks passed

arsenm deleted the users/arsenm/amdgpu/fix-vgpr-mfma-dead-vni-crash branch August 16, 2025 14:09

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AMDGPU: Fix crash in rewrite AGPR copy MFMA pass on dead valnos #153915

AMDGPU: Fix crash in rewrite AGPR copy MFMA pass on dead valnos #153915

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AMDGPU: Fix crash in rewrite AGPR copy MFMA pass on dead valnos #153915

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arsenm commented Aug 16, 2025

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