[llvm] [DAG] Remove restrictions and increase optimization opportunities (PR #68972)

[via llvm-commits]

https://github.com/LiqinWeng updated https://github.com/llvm/llvm-project/pull/68972

>From 231dde8bbd07ab392fa67a22e3d18caf72e5769e Mon Sep 17 00:00:00 2001
From: "liqin.weng" <liqin.weng at spacemit.com>
Date: Fri, 13 Oct 2023 17:57:53 +0800
Subject: [PATCH] [DAG] Remove restrictions and increase optimization
 opportunities

this patch remove the restriction for folding (shl (sext (add_nsw x, c1)), c2) -> (add (shl (sext x), c2), c1 << c2), and test case from dhrystone
, see this link: https://godbolt.org/z/5KnjK16oG
---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp |  3 +-
 .../CodeGen/RISCV/riscv-shifted-extend.ll     | 63 +++++++++++++++++++
 2 files changed, 64 insertions(+), 2 deletions(-)
 create mode 100644 llvm/test/CodeGen/RISCV/riscv-shifted-extend.ll

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 1021b07da1ac6c5..14cc9008c7e3895 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10045,8 +10045,7 @@ SDValue DAGCombiner::visitSHL(SDNode *N) {
   // TODO: Should we limit this with isLegalAddImmediate?
   if (N0.getOpcode() == ISD::SIGN_EXTEND &&
       N0.getOperand(0).getOpcode() == ISD::ADD &&
-      N0.getOperand(0)->getFlags().hasNoSignedWrap() && N0->hasOneUse() &&
-      N0.getOperand(0)->hasOneUse() &&
+      N0.getOperand(0)->getFlags().hasNoSignedWrap() &&
       TLI.isDesirableToCommuteWithShift(N, Level)) {
     SDValue Add = N0.getOperand(0);
     SDLoc DL(N0);
diff --git a/llvm/test/CodeGen/RISCV/riscv-shifted-extend.ll b/llvm/test/CodeGen/RISCV/riscv-shifted-extend.ll
new file mode 100644
index 000000000000000..f73377f1afd9838
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/riscv-shifted-extend.ll
@@ -0,0 +1,63 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 3
+; RUN: llc -mtriple=riscv64 -verify-machineinstrs < %s \
+; RUN:   | FileCheck -check-prefix=RV64 %s
+
+define void @test(ptr nocapture noundef writeonly %array1, i32 noundef signext %a, i32 noundef signext %b) {
+; RV64-LABEL: test:
+; RV64:       # %bb.0: # %entry
+; RV64-NEXT:    addiw a3, a1, 5
+; RV64-NEXT:    slli a1, a1, 2
+; RV64-NEXT:    add a0, a1, a0
+; RV64-NEXT:    sw a2, 20(a0)
+; RV64-NEXT:    sw a2, 24(a0)
+; RV64-NEXT:    sw a3, 140(a0)
+; RV64-NEXT:    ret
+entry:
+  %add = add nsw i32 %a, 5
+  %idxprom = sext i32 %add to i64
+  %arrayidx = getelementptr inbounds i32, ptr %array1, i64 %idxprom
+  store i32 %b, ptr %arrayidx, align 4
+  %add3 = add nsw i32 %a, 6
+  %idxprom4 = sext i32 %add3 to i64
+  %arrayidx5 = getelementptr inbounds i32, ptr %array1, i64 %idxprom4
+  store i32 %b, ptr %arrayidx5, align 4
+  %add6 = add nsw i32 %a, 35
+  %idxprom7 = sext i32 %add6 to i64
+  %arrayidx8 = getelementptr inbounds i32, ptr %array1, i64 %idxprom7
+  store i32 %add, ptr %arrayidx8, align 4
+  ret void
+}
+
+; test of jumpping, find add's operand has one more use can simplified
+define void @test1(ptr nocapture noundef %array1, i32 noundef signext %a, i32 noundef signext %b, i32 noundef signext %x) {
+; RV64-LABEL: test1:
+; RV64:       # %bb.0: # %entry
+; RV64-NEXT:    addiw a4, a1, 5
+; RV64-NEXT:    mv a5, a4
+; RV64-NEXT:    bgtz a3, .LBB1_2
+; RV64-NEXT:  # %bb.1: # %entry
+; RV64-NEXT:    mv a5, a2
+; RV64-NEXT:  .LBB1_2: # %entry
+; RV64-NEXT:    slli a1, a1, 2
+; RV64-NEXT:    add a0, a1, a0
+; RV64-NEXT:    sw a5, 20(a0)
+; RV64-NEXT:    sw a5, 24(a0)
+; RV64-NEXT:    sw a4, 140(a0)
+; RV64-NEXT:    ret
+entry:
+  %add = add nsw i32 %a, 5
+  %cmp = icmp sgt i32 %x, 0
+  %idxprom = sext i32 %add to i64
+  %arrayidx = getelementptr inbounds i32, ptr %array1, i64 %idxprom
+  %add.b = select i1 %cmp, i32 %add, i32 %b
+  store i32 %add.b, ptr %arrayidx, align 4
+  %add5 = add nsw i32 %a, 6
+  %idxprom6 = sext i32 %add5 to i64
+  %arrayidx7 = getelementptr inbounds i32, ptr %array1, i64 %idxprom6
+  store i32 %add.b, ptr %arrayidx7, align 4
+  %add8 = add nsw i32 %a, 35
+  %idxprom9 = sext i32 %add8 to i64
+  %arrayidx10 = getelementptr inbounds i32, ptr %array1, i64 %idxprom9
+  store i32 %add, ptr %arrayidx10, align 4
+  ret void
+}