[llvm] f8416fc - [RISCV][VLOPT] Look through PHI instructions (#132236)
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Mon Mar 24 06:26:13 PDT 2025
Author: Michael Maitland
Date: 2025-03-24T09:26:09-04:00
New Revision: f8416fcfeca09f0b2c1522e89eaebcbdc0a9f2d3
URL: https://github.com/llvm/llvm-project/commit/f8416fcfeca09f0b2c1522e89eaebcbdc0a9f2d3
DIFF: https://github.com/llvm/llvm-project/commit/f8416fcfeca09f0b2c1522e89eaebcbdc0a9f2d3.diff
LOG: [RISCV][VLOPT] Look through PHI instructions (#132236)
Similar to what we do for copies. We may reduce one of the PHI operands
and not the other, and thats perfectly okay.
Added:
Modified:
llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp
llvm/test/CodeGen/RISCV/rvv/vl-opt.mir
Removed:
################################################################################
diff --git a/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp b/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp
index c36a1e9adccb0..9ed2ba274bc53 100644
--- a/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp
+++ b/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp
@@ -1323,6 +1323,7 @@ std::optional<MachineOperand>
RISCVVLOptimizer::checkUsers(const MachineInstr &MI) const {
std::optional<MachineOperand> CommonVL;
SmallSetVector<MachineOperand *, 8> Worklist;
+ SmallPtrSet<const MachineInstr *, 4> PHISeen;
for (auto &UserOp : MRI->use_operands(MI.getOperand(0).getReg()))
Worklist.insert(&UserOp);
@@ -1340,6 +1341,16 @@ RISCVVLOptimizer::checkUsers(const MachineInstr &MI) const {
continue;
}
+ if (UserMI.isPHI()) {
+ // Don't follow PHI cycles
+ if (!PHISeen.insert(&UserMI).second)
+ continue;
+ LLVM_DEBUG(dbgs() << " Peeking through uses of PHI\n");
+ for (auto &PhiUse : MRI->use_operands(UserMI.getOperand(0).getReg()))
+ Worklist.insert(&PhiUse);
+ continue;
+ }
+
auto VLOp = getMinimumVLForUser(UserOp);
if (!VLOp)
return std::nullopt;
diff --git a/llvm/test/CodeGen/RISCV/rvv/vl-opt.mir b/llvm/test/CodeGen/RISCV/rvv/vl-opt.mir
index d42feeca9dbcc..6343afc6bac62 100644
--- a/llvm/test/CodeGen/RISCV/rvv/vl-opt.mir
+++ b/llvm/test/CodeGen/RISCV/rvv/vl-opt.mir
@@ -368,3 +368,134 @@ body: |
%y:vr = COPY %x
%z:vr = PseudoVADD_VV_M1 $noreg, %y, $noreg, 1, 4 /* e16 */, 0 /* tu, mu */
...
+---
+name: phi
+tracksRegLiveness: true
+body: |
+ ; CHECK-LABEL: name: phi
+ ; CHECK: bb.0:
+ ; CHECK-NEXT: successors: %bb.2(0x40000000), %bb.1(0x40000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: %w:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+ ; CHECK-NEXT: BNE $noreg, $noreg, %bb.2
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.1:
+ ; CHECK-NEXT: successors: %bb.2(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.2:
+ ; CHECK-NEXT: %y:vr = PHI %w, %bb.0, %x, %bb.1
+ ; CHECK-NEXT: %z:vr = PseudoVADD_VV_M1 $noreg, %y, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+ bb.0:
+ %w:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
+ BNE $noreg, $noreg, %bb.2
+ bb.1:
+ %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
+ bb.2:
+ %y:vr = PHI %w, %bb.0, %x, %bb.1
+ %z:vr = PseudoVADD_VV_M1 $noreg, %y, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+...
+---
+name: phi_user_invalid_sew
+tracksRegLiveness: true
+body: |
+ ; CHECK-LABEL: name: phi_user_invalid_sew
+ ; CHECK: bb.0:
+ ; CHECK-NEXT: successors: %bb.2(0x40000000), %bb.1(0x40000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: %w:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
+ ; CHECK-NEXT: BNE $noreg, $noreg, %bb.2
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.1:
+ ; CHECK-NEXT: successors: %bb.2(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.2:
+ ; CHECK-NEXT: %y:vr = PHI %w, %bb.0, %x, %bb.1
+ ; CHECK-NEXT: %z:vr = PseudoVADD_VV_M1 $noreg, %y, $noreg, 1, 4 /* e16 */, 0 /* tu, mu */
+ bb.0:
+ %w:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
+ BNE $noreg, $noreg, %bb.2
+ bb.1:
+ %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
+ bb.2:
+ %y:vr = PHI %w, %bb.0, %x, %bb.1
+ %z:vr = PseudoVADD_VV_M1 $noreg, %y, $noreg, 1, 4 /* e16 */, 0 /* tu, mu */
+...
+---
+name: phi_
diff erent_incoming_sew
+tracksRegLiveness: true
+body: |
+ ; CHECK-LABEL: name: phi_
diff erent_incoming_sew
+ ; CHECK: bb.0:
+ ; CHECK-NEXT: successors: %bb.2(0x40000000), %bb.1(0x40000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: %w:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+ ; CHECK-NEXT: BNE $noreg, $noreg, %bb.2
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.1:
+ ; CHECK-NEXT: successors: %bb.2(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 4 /* e16 */, 0 /* tu, mu */
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.2:
+ ; CHECK-NEXT: %y:vr = PHI %w, %bb.0, %x, %bb.1
+ ; CHECK-NEXT: %z:vr = PseudoVADD_VV_M1 $noreg, %y, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+ bb.0:
+ %w:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
+ BNE $noreg, $noreg, %bb.2
+ bb.1:
+ %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 4 /* e16 */, 0 /* tu, mu */
+ bb.2:
+ %y:vr = PHI %w, %bb.0, %x, %bb.1
+ %z:vr = PseudoVADD_VV_M1 $noreg, %y, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+...
+---
+name: phi_cycle_direct
+tracksRegLiveness: true
+body: |
+ ; CHECK-LABEL: name: phi_cycle_direct
+ ; CHECK: bb.0:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.1:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: %y:vr = PHI %x, %bb.0, %y, %bb.1
+ ; CHECK-NEXT: %z:vr = PseudoVADD_VV_M1 $noreg, %y, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+ ; CHECK-NEXT: PseudoBR %bb.1
+ bb.0:
+ %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
+ bb.1:
+ %y:vr = PHI %x, %bb.0, %y, %bb.1
+ %z:vr = PseudoVADD_VV_M1 $noreg, %y, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+ PseudoBR %bb.1
+...
+---
+name: phi_cycle_indirect
+tracksRegLiveness: true
+body: |
+ ; CHECK-LABEL: name: phi_cycle_indirect
+ ; CHECK: bb.0:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.1:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: %y:vr = PHI %x, %bb.0, %z, %bb.1
+ ; CHECK-NEXT: %z:vr = PseudoVADD_VV_M1 $noreg, %y, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+ ; CHECK-NEXT: PseudoBR %bb.1
+ bb.0:
+ %x:vr = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, -1, 3 /* e8 */, 0 /* tu, mu */
+ bb.1:
+ %y:vr = PHI %x, %bb.0, %z, %bb.1
+ %z:vr = PseudoVADD_VV_M1 $noreg, %y, $noreg, 1, 3 /* e8 */, 0 /* tu, mu */
+ PseudoBR %bb.1
+...
+
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