[llvm] db782b4 - [RISCV] Don't forward AVL in VSETVLIInfo if it would clobber other definitions (#97264)
via llvm-commits
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Thu Jul 4 20:45:04 PDT 2024
Author: Luke Lau
Date: 2024-07-05T11:44:59+08:00
New Revision: db782b44b3471c0ab41950c3f79d0ea7b916c135
URL: https://github.com/llvm/llvm-project/commit/db782b44b3471c0ab41950c3f79d0ea7b916c135
DIFF: https://github.com/llvm/llvm-project/commit/db782b44b3471c0ab41950c3f79d0ea7b916c135.diff
LOG: [RISCV] Don't forward AVL in VSETVLIInfo if it would clobber other definitions (#97264)
This fixes a crash found when compiling OpenBLAS with -mllvm
-verify-machineinstrs.
When we "forward" the AVL from the output of a vsetvli, we might have to
extend the LiveInterval of the AVL to where insert the new vsetvli.
Most of the time we are able to extend the LiveInterval because there's
only one val num (definition) for the register. But PHI elimination can
assign multiple values to the same register, in which case we end up
clobbering a different val num when extending:
%x = PseudoVSETVLI %avl, ...
%avl = ADDI ...
%v = PseudoVADD ..., avl=%x
; %avl is forwarded to PseudoVADD:
%x = PseudoVSETVLI %avl, ...
%avl = ADDI ...
%v = PseudoVADD ..., avl=%avl
Here there's no way to extend the %avl from the vsetvli since %avl is
redefined, i.e. we have two val nums.
This fixes it by only forwarding it when we have exactly one val num,
where it should be safe to extend it.
Added:
Modified:
llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.ll
llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.mir
llvm/test/Transforms/LoopStrengthReduce/RISCV/lsr-drop-solution.ll
Removed:
################################################################################
diff --git a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp b/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
index a1ae8a1250813..9c76bb15035eb 100644
--- a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
+++ b/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
@@ -956,6 +956,12 @@ void RISCVInsertVSETVLI::forwardVSETVLIAVL(VSETVLIInfo &Info) const {
VSETVLIInfo DefInstrInfo = getInfoForVSETVLI(*DefMI);
if (!DefInstrInfo.hasSameVLMAX(Info))
return;
+ // If the AVL is a register with multiple definitions, don't forward it. We
+ // might not be able to extend its LiveInterval without clobbering other val
+ // nums.
+ if (DefInstrInfo.hasAVLReg() &&
+ !LIS->getInterval(DefInstrInfo.getAVLReg()).containsOneValue())
+ return;
Info.setAVL(DefInstrInfo);
}
diff --git a/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.ll b/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.ll
index 701192839d6aa..f93022c9d132d 100644
--- a/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.ll
+++ b/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.ll
@@ -1125,3 +1125,39 @@ exit:
call void @llvm.riscv.vse.nxv8i8(<vscale x 8 x i8> %1, ptr %p, i64 1)
ret void
}
+
+; Check that we don't forward an AVL if we wouldn't be able to extend its
+; LiveInterval without clobbering other val nos.
+define <vscale x 4 x i32> @unforwardable_avl(i64 %n, <vscale x 4 x i32> %v, i1 %cmp) {
+; CHECK-LABEL: unforwardable_avl:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: vsetvli a2, a0, e32, m2, ta, ma
+; CHECK-NEXT: andi a1, a1, 1
+; CHECK-NEXT: .LBB27_1: # %for.body
+; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT: addi a0, a0, 1
+; CHECK-NEXT: bnez a1, .LBB27_1
+; CHECK-NEXT: # %bb.2: # %for.cond.cleanup
+; CHECK-NEXT: vsetvli a0, zero, e32, m2, ta, ma
+; CHECK-NEXT: vadd.vv v10, v8, v8
+; CHECK-NEXT: vsetvli zero, a2, e32, m2, ta, ma
+; CHECK-NEXT: vadd.vv v8, v10, v8
+; CHECK-NEXT: ret
+entry:
+ %0 = tail call i64 @llvm.riscv.vsetvli.i64(i64 %n, i64 2, i64 1)
+ br label %for.body
+
+for.body:
+ ; Use %n in a PHI here so its virtual register is assigned to a second time here.
+ %1 = phi i64 [ %3, %for.body ], [ %n, %entry ]
+ %2 = tail call i64 @llvm.riscv.vsetvli.i64(i64 %1, i64 0, i64 0)
+ %3 = add i64 %1, 1
+ br i1 %cmp, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:
+ %4 = tail call <vscale x 4 x i32> @llvm.riscv.vadd.nxv2f32.nxv2f32.i64(<vscale x 4 x i32> undef, <vscale x 4 x i32> %v, <vscale x 4 x i32> %v, i64 -1)
+ ; VL toggle needed here: If the %n AVL was forwarded here we wouldn't be able
+ ; to extend it's LiveInterval because it would clobber the assignment at %1.
+ %5 = tail call <vscale x 4 x i32> @llvm.riscv.vadd.nxv2f32.nxv2f32.i64(<vscale x 4 x i32> undef, <vscale x 4 x i32> %4, <vscale x 4 x i32> %v, i64 %0)
+ ret <vscale x 4 x i32> %5
+}
diff --git a/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.mir b/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.mir
index 4091d1711b584..ee10c9987be49 100644
--- a/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.mir
+++ b/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.mir
@@ -134,6 +134,10 @@
ret void
}
+ define void @unforwardable_avl() {
+ ret void
+ }
+
declare i32 @llvm.vector.reduce.add.v4i32(<4 x i32>)
declare <vscale x 1 x i64> @llvm.riscv.vadd.nxv1i64.nxv1i64.i64(<vscale x 1 x i64>, <vscale x 1 x i64>, <vscale x 1 x i64>, i64) #1
@@ -990,3 +994,43 @@ body: |
%x:gpr = PseudoVMV_X_S undef $noreg, 6
PseudoBR %bb.1
...
+---
+name: unforwardable_avl
+tracksRegLiveness: true
+body: |
+ ; CHECK-LABEL: name: unforwardable_avl
+ ; CHECK: bb.0:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: liveins: $x10, $v8m2
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: %avl:gprnox0 = COPY $x10
+ ; CHECK-NEXT: %outvl:gprnox0 = PseudoVSETVLI %avl, 209 /* e32, m2, ta, ma */, implicit-def $vl, implicit-def $vtype
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.1:
+ ; CHECK-NEXT: successors: %bb.2(0x80000000)
+ ; CHECK-NEXT: liveins: $v8m2
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: dead %avl:gprnox0 = ADDI %avl, 1
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.2:
+ ; CHECK-NEXT: liveins: $v8m2
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: dead [[PseudoVSETVLIX0_:%[0-9]+]]:gpr = PseudoVSETVLIX0 killed $x0, 209 /* e32, m2, ta, ma */, implicit-def $vl, implicit-def $vtype
+ ; CHECK-NEXT: renamable $v10m2 = PseudoVADD_VV_M2 undef renamable $v10m2, renamable $v8m2, renamable $v8m2, -1, 5 /* e32 */, 0 /* tu, mu */, implicit $vl, implicit $vtype
+ ; CHECK-NEXT: dead $x0 = PseudoVSETVLI %outvl, 209 /* e32, m2, ta, ma */, implicit-def $vl, implicit-def $vtype
+ ; CHECK-NEXT: renamable $v8m2 = PseudoVADD_VV_M2 undef renamable $v8m2, killed renamable $v10m2, renamable $v8m2, $noreg, 5 /* e32 */, 0 /* tu, mu */, implicit $vl, implicit $vtype
+ ; CHECK-NEXT: PseudoRET implicit $v8m2
+ bb.0:
+ liveins: $x10, $v8m2
+ %avl:gprnox0 = COPY $x10
+ %outvl:gprnox0 = PseudoVSETVLI %avl:gprnox0, 209, implicit-def dead $vl, implicit-def dead $vtype
+
+ bb.1:
+ liveins: $v8m2
+ %avl:gprnox0 = ADDI %avl:gprnox0, 1
+
+ bb.2:
+ liveins: $v8m2
+ renamable $v10m2 = PseudoVADD_VV_M2 undef renamable $v10m2, renamable $v8m2, renamable $v8m2, -1, 5, 0
+ renamable $v8m2 = PseudoVADD_VV_M2 undef renamable $v8m2, killed renamable $v10m2, killed renamable $v8m2, %outvl:gprnox0, 5, 0
+ PseudoRET implicit $v8m2
diff --git a/llvm/test/Transforms/LoopStrengthReduce/RISCV/lsr-drop-solution.ll b/llvm/test/Transforms/LoopStrengthReduce/RISCV/lsr-drop-solution.ll
index 7353acd7228cd..1ab19081b7de5 100644
--- a/llvm/test/Transforms/LoopStrengthReduce/RISCV/lsr-drop-solution.ll
+++ b/llvm/test/Transforms/LoopStrengthReduce/RISCV/lsr-drop-solution.ll
@@ -20,6 +20,7 @@ define ptr @foo(ptr %a0, ptr %a1, i64 %a2) {
; CHECK-NEXT: mv a3, a0
; CHECK-NEXT: .LBB0_3: # %do.body
; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT: vsetvli zero, a4, e8, m8, ta, ma
; CHECK-NEXT: vle8.v v8, (a1)
; CHECK-NEXT: vse8.v v8, (a3)
; CHECK-NEXT: add a3, a3, a4
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