[llvm] [DAGCombiner] Add basic support for `trunc nsw/nuw` (PR #113808)
via llvm-commits
llvm-commits at lists.llvm.org
Sun Oct 27 07:26:08 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-selectiondag
@llvm/pr-subscribers-backend-aarch64
Author: Yingwei Zheng (dtcxzyw)
<details>
<summary>Changes</summary>
This patch adds basic support for `trunc nsw/nuw` in SDAG. It will allow DAGCombiner to further eliminate in-reg `zext/sext` instructions.
---
Full diff: https://github.com/llvm/llvm-project/pull/113808.diff
5 Files Affected:
- (modified) llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (+27-27)
- (modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (+7-1)
- (added) llvm/test/CodeGen/AArch64/trunc-nsw-nuw.ll (+60)
- (added) llvm/test/CodeGen/RISCV/trunc-nsw-nuw.ll (+78)
- (added) llvm/test/CodeGen/X86/trunc-nsw-nuw.ll (+58)
``````````diff
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index ad2d2ede302af8..0b249f2f7267bd 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2329,6 +2329,8 @@ static bool isTruncateOf(SelectionDAG &DAG, SDValue N, SDValue &Op,
if (N->getOpcode() == ISD::TRUNCATE) {
Op = N->getOperand(0);
Known = DAG.computeKnownBits(Op);
+ if (N->getFlags().hasNoUnsignedWrap())
+ Known.Zero.setBitsFrom(N.getScalarValueSizeInBits());
return true;
}
@@ -13793,23 +13795,22 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
unsigned OpBits = Op.getScalarValueSizeInBits();
unsigned MidBits = N0.getScalarValueSizeInBits();
unsigned DestBits = VT.getScalarSizeInBits();
- unsigned NumSignBits = DAG.ComputeNumSignBits(Op);
- if (OpBits == DestBits) {
- // Op is i32, Mid is i8, and Dest is i32. If Op has more than 24 sign
- // bits, it is already ready.
- if (NumSignBits > DestBits-MidBits)
+ if (N0->getFlags().hasNoSignedWrap() ||
+ DAG.ComputeNumSignBits(Op) > OpBits - MidBits) {
+ if (OpBits == DestBits) {
+ // Op is i32, Mid is i8, and Dest is i32. If Op has more than 24 sign
+ // bits, it is already ready.
return Op;
- } else if (OpBits < DestBits) {
- // Op is i32, Mid is i8, and Dest is i64. If Op has more than 24 sign
- // bits, just sext from i32.
- if (NumSignBits > OpBits-MidBits)
+ } else if (OpBits < DestBits) {
+ // Op is i32, Mid is i8, and Dest is i64. If Op has more than 24 sign
+ // bits, just sext from i32.
return DAG.getNode(ISD::SIGN_EXTEND, DL, VT, Op);
- } else {
- // Op is i64, Mid is i8, and Dest is i32. If Op has more than 56 sign
- // bits, just truncate to i32.
- if (NumSignBits > OpBits-MidBits)
+ } else {
+ // Op is i64, Mid is i8, and Dest is i32. If Op has more than 56 sign
+ // bits, just truncate to i32.
return DAG.getNode(ISD::TRUNCATE, DL, VT, Op);
+ }
}
// fold (sext (truncate x)) -> (sextinreg x).
@@ -14083,24 +14084,23 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
unsigned OpBits = SrcVT.getScalarSizeInBits();
unsigned MidBits = MinVT.getScalarSizeInBits();
unsigned DestBits = VT.getScalarSizeInBits();
- unsigned NumSignBits = DAG.ComputeNumSignBits(Op);
- if (OpBits == DestBits) {
- // Op is i32, Mid is i8, and Dest is i32. If Op has more than 24 sign
- // bits, it is already ready.
- if (NumSignBits > DestBits - MidBits)
+ if (N0->getFlags().hasNoSignedWrap() ||
+ DAG.ComputeNumSignBits(Op) > OpBits - MidBits) {
+ if (OpBits == DestBits) {
+ // Op is i32, Mid is i8, and Dest is i32. If Op has more than 24 sign
+ // bits, it is already ready.
return Op;
- } else if (OpBits < DestBits) {
- // Op is i32, Mid is i8, and Dest is i64. If Op has more than 24 sign
- // bits, just sext from i32.
- // FIXME: This can probably be ZERO_EXTEND nneg?
- if (NumSignBits > OpBits - MidBits)
+ } else if (OpBits < DestBits) {
+ // Op is i32, Mid is i8, and Dest is i64. If Op has more than 24 sign
+ // bits, just sext from i32.
+ // FIXME: This can probably be ZERO_EXTEND nneg?
return DAG.getNode(ISD::SIGN_EXTEND, DL, VT, Op);
- } else {
- // Op is i64, Mid is i8, and Dest is i32. If Op has more than 56 sign
- // bits, just truncate to i32.
- if (NumSignBits > OpBits - MidBits)
+ } else {
+ // Op is i64, Mid is i8, and Dest is i32. If Op has more than 56 sign
+ // bits, just truncate to i32.
return DAG.getNode(ISD::TRUNCATE, DL, VT, Op);
+ }
}
}
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 8450553743074c..e1e4db79627ef6 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3823,7 +3823,13 @@ void SelectionDAGBuilder::visitTrunc(const User &I) {
SDValue N = getValue(I.getOperand(0));
EVT DestVT = DAG.getTargetLoweringInfo().getValueType(DAG.getDataLayout(),
I.getType());
- setValue(&I, DAG.getNode(ISD::TRUNCATE, getCurSDLoc(), DestVT, N));
+ SDNodeFlags Flags;
+ if (auto *Trunc = dyn_cast<TruncInst>(&I)) {
+ Flags.setNoSignedWrap(Trunc->hasNoSignedWrap());
+ Flags.setNoUnsignedWrap(Trunc->hasNoUnsignedWrap());
+ }
+
+ setValue(&I, DAG.getNode(ISD::TRUNCATE, getCurSDLoc(), DestVT, N, Flags));
}
void SelectionDAGBuilder::visitZExt(const User &I) {
diff --git a/llvm/test/CodeGen/AArch64/trunc-nsw-nuw.ll b/llvm/test/CodeGen/AArch64/trunc-nsw-nuw.ll
new file mode 100644
index 00000000000000..6041db74639f32
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/trunc-nsw-nuw.ll
@@ -0,0 +1,60 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s -mtriple=aarch64-- | FileCheck %s
+
+define zeroext i32 @trunc_nuw_nsw_urem(i64 %x) nounwind {
+; CHECK-LABEL: trunc_nuw_nsw_urem:
+; CHECK: // %bb.0: // %entry
+; CHECK-NEXT: mov w8, #5977 // =0x1759
+; CHECK-NEXT: mov w9, #10000 // =0x2710
+; CHECK-NEXT: movk w8, #53687, lsl #16
+; CHECK-NEXT: mul x8, x0, x8
+; CHECK-NEXT: lsr x8, x8, #45
+; CHECK-NEXT: msub w0, w8, w9, w0
+; CHECK-NEXT: ret
+entry:
+ %trunc = trunc nuw nsw i64 %x to i32
+ %rem = urem i32 %trunc, 10000
+ ret i32 %rem
+}
+
+define i64 @zext_nneg_udiv_trunc_nuw(i64 %x) nounwind {
+; CHECK-LABEL: zext_nneg_udiv_trunc_nuw:
+; CHECK: // %bb.0: // %entry
+; CHECK-NEXT: mov w8, #52429 // =0xcccd
+; CHECK-NEXT: mul w8, w0, w8
+; CHECK-NEXT: lsr w0, w8, #23
+; CHECK-NEXT: ret
+entry:
+ %trunc = trunc nuw i64 %x to i16
+ %div = udiv i16 %trunc, 160
+ %ext = zext nneg i16 %div to i64
+ ret i64 %ext
+}
+
+define i64 @sext_udiv_trunc_nuw(i64 %x) nounwind {
+; CHECK-LABEL: sext_udiv_trunc_nuw:
+; CHECK: // %bb.0: // %entry
+; CHECK-NEXT: mov w8, #52429 // =0xcccd
+; CHECK-NEXT: mul w8, w0, w8
+; CHECK-NEXT: lsr w0, w8, #23
+; CHECK-NEXT: ret
+entry:
+ %trunc = trunc nuw i64 %x to i16
+ %div = udiv i16 %trunc, 160
+ %ext = sext i16 %div to i64
+ ret i64 %ext
+}
+
+define ptr @gep_nusw_zext_nneg_add_trunc_nuw_nsw(ptr %p, i64 %x) nounwind {
+; CHECK-LABEL: gep_nusw_zext_nneg_add_trunc_nuw_nsw:
+; CHECK: // %bb.0: // %entry
+; CHECK-NEXT: add w8, w1, #5
+; CHECK-NEXT: add x0, x0, w8, uxtw #2
+; CHECK-NEXT: ret
+entry:
+ %trunc = trunc nuw nsw i64 %x to i32
+ %add = add nuw nsw i32 %trunc, 5
+ %offset = zext nneg i32 %add to i64
+ %gep = getelementptr nusw float, ptr %p, i64 %offset
+ ret ptr %gep
+}
diff --git a/llvm/test/CodeGen/RISCV/trunc-nsw-nuw.ll b/llvm/test/CodeGen/RISCV/trunc-nsw-nuw.ll
new file mode 100644
index 00000000000000..f270775adcc155
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/trunc-nsw-nuw.ll
@@ -0,0 +1,78 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s -mtriple=riscv64 -mattr=+m | FileCheck %s
+
+define signext i8 @trunc_nsw_add(i32 signext %x) nounwind {
+; CHECK-LABEL: trunc_nsw_add:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: addiw a0, a0, 1
+; CHECK-NEXT: ret
+entry:
+ %add = add nsw i32 %x, 1
+ %trunc = trunc nsw i32 %add to i8
+ ret i8 %trunc
+}
+
+define signext i32 @trunc_nuw_nsw_urem(i64 %x) nounwind {
+; CHECK-LABEL: trunc_nuw_nsw_urem:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: lui a1, 210
+; CHECK-NEXT: addiw a1, a1, -1167
+; CHECK-NEXT: slli a1, a1, 12
+; CHECK-NEXT: addi a1, a1, 1881
+; CHECK-NEXT: mul a1, a0, a1
+; CHECK-NEXT: srli a1, a1, 45
+; CHECK-NEXT: lui a2, 2
+; CHECK-NEXT: addi a2, a2, 1808
+; CHECK-NEXT: mul a1, a1, a2
+; CHECK-NEXT: subw a0, a0, a1
+; CHECK-NEXT: ret
+entry:
+ %trunc = trunc nuw nsw i64 %x to i32
+ %rem = urem i32 %trunc, 10000
+ ret i32 %rem
+}
+
+define i64 @zext_nneg_udiv_trunc_nuw(i64 %x) nounwind {
+; CHECK-LABEL: zext_nneg_udiv_trunc_nuw:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: lui a1, 13
+; CHECK-NEXT: addi a1, a1, -819
+; CHECK-NEXT: mul a0, a0, a1
+; CHECK-NEXT: srliw a0, a0, 23
+; CHECK-NEXT: ret
+entry:
+ %trunc = trunc nuw i64 %x to i16
+ %div = udiv i16 %trunc, 160
+ %ext = zext nneg i16 %div to i64
+ ret i64 %ext
+}
+
+define i64 @sext_udiv_trunc_nuw(i64 %x) nounwind {
+; CHECK-LABEL: sext_udiv_trunc_nuw:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: lui a1, 13
+; CHECK-NEXT: addi a1, a1, -819
+; CHECK-NEXT: mul a0, a0, a1
+; CHECK-NEXT: srliw a0, a0, 23
+; CHECK-NEXT: ret
+entry:
+ %trunc = trunc nuw i64 %x to i16
+ %div = udiv i16 %trunc, 160
+ %ext = sext i16 %div to i64
+ ret i64 %ext
+}
+
+define ptr @gep_nusw_zext_nneg_add_trunc_nuw_nsw(ptr %p, i64 %x) nounwind {
+; CHECK-LABEL: gep_nusw_zext_nneg_add_trunc_nuw_nsw:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: slli a1, a1, 2
+; CHECK-NEXT: add a0, a1, a0
+; CHECK-NEXT: addi a0, a0, 20
+; CHECK-NEXT: ret
+entry:
+ %trunc = trunc nuw nsw i64 %x to i32
+ %add = add nuw nsw i32 %trunc, 5
+ %offset = zext nneg i32 %add to i64
+ %gep = getelementptr nusw float, ptr %p, i64 %offset
+ ret ptr %gep
+}
diff --git a/llvm/test/CodeGen/X86/trunc-nsw-nuw.ll b/llvm/test/CodeGen/X86/trunc-nsw-nuw.ll
new file mode 100644
index 00000000000000..40b48bec8fffd7
--- /dev/null
+++ b/llvm/test/CodeGen/X86/trunc-nsw-nuw.ll
@@ -0,0 +1,58 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s -mtriple=x86_64 | FileCheck %s
+
+define zeroext i32 @trunc_nuw_nsw_urem(i64 %x) nounwind {
+; CHECK-LABEL: trunc_nuw_nsw_urem:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: movq %rdi, %rax
+; CHECK-NEXT: movl $3518437209, %ecx # imm = 0xD1B71759
+; CHECK-NEXT: imulq %rdi, %rcx
+; CHECK-NEXT: shrq $45, %rcx
+; CHECK-NEXT: imull $10000, %ecx, %ecx # imm = 0x2710
+; CHECK-NEXT: subl %ecx, %eax
+; CHECK-NEXT: # kill: def $eax killed $eax killed $rax
+; CHECK-NEXT: retq
+entry:
+ %trunc = trunc nuw nsw i64 %x to i32
+ %rem = urem i32 %trunc, 10000
+ ret i32 %rem
+}
+
+define i64 @zext_nneg_udiv_trunc_nuw(i64 %x) nounwind {
+; CHECK-LABEL: zext_nneg_udiv_trunc_nuw:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: imull $52429, %edi, %eax # imm = 0xCCCD
+; CHECK-NEXT: shrl $23, %eax
+; CHECK-NEXT: retq
+entry:
+ %trunc = trunc nuw i64 %x to i16
+ %div = udiv i16 %trunc, 160
+ %ext = zext nneg i16 %div to i64
+ ret i64 %ext
+}
+
+define i64 @sext_udiv_trunc_nuw(i64 %x) nounwind {
+; CHECK-LABEL: sext_udiv_trunc_nuw:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: imull $52429, %edi, %eax # imm = 0xCCCD
+; CHECK-NEXT: shrl $23, %eax
+; CHECK-NEXT: retq
+entry:
+ %trunc = trunc nuw i64 %x to i16
+ %div = udiv i16 %trunc, 160
+ %ext = sext i16 %div to i64
+ ret i64 %ext
+}
+
+define ptr @gep_nusw_zext_nneg_add_trunc_nuw_nsw(ptr %p, i64 %x) nounwind {
+; CHECK-LABEL: gep_nusw_zext_nneg_add_trunc_nuw_nsw:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: leaq 20(%rdi,%rsi,4), %rax
+; CHECK-NEXT: retq
+entry:
+ %trunc = trunc nuw nsw i64 %x to i32
+ %add = add nuw nsw i32 %trunc, 5
+ %offset = zext nneg i32 %add to i64
+ %gep = getelementptr nusw float, ptr %p, i64 %offset
+ ret ptr %gep
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/113808
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