[RISCV] Limit (and (sra x, c2), c1) -> (srli (srai x, c2-c3), c3) isel in some cases.

[topperc]

If x is a shl by 32 and c1 is an simm12, we would prefer to use a SRAIW+ANDI. This prevents selecting the slli to a separate slli instruction.

Fixes regression from #101868

[llvmbot]

@llvm/pr-subscribers-backend-risc-v

Author: Craig Topper (topperc)

Changes

If x is a shl by 32 and c1 is an simm12, we would prefer to use a SRAIW+ANDI. This prevents selecting the slli to a separate slli instruction.

---

Full diff: https://github.com/llvm/llvm-project/pull/102034.diff

2 Files Affected:

• (modified) llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp (+5-1)
• (modified) llvm/test/CodeGen/RISCV/selectcc-to-shiftand.ll (+2-3)

diff --git a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
index 3dcfeecec1e75..b140d72e36fed 100644
--- a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -1460,7 +1460,11 @@ void RISCVDAGToDAGISel::Select(SDNode *Node) {
 
       SDValue X = N0.getOperand(0);
 
-      if (isMask_64(C1)) {
+      // Prefer SRAIW + ANDI when possible.
+      bool Skip = C2 > 32 && IsC1ANDI && X.getOpcode() == ISD::SHL &&
+                  isa<ConstantSDNode>(X.getOperand(1)) &&
+                  X.getConstantOperandVal(1) == 32;
+      if (isMask_64(C1) && !Skip) {
         unsigned Leading = XLen - llvm::bit_width(C1);
         if (C2 > Leading) {
           SDNode *SRAI = CurDAG->getMachineNode(
diff --git a/llvm/test/CodeGen/RISCV/selectcc-to-shiftand.ll b/llvm/test/CodeGen/RISCV/selectcc-to-shiftand.ll
index 4749cc656693c..0d96fbfa81279 100644
--- a/llvm/test/CodeGen/RISCV/selectcc-to-shiftand.ll
+++ b/llvm/test/CodeGen/RISCV/selectcc-to-shiftand.ll
@@ -276,9 +276,8 @@ define i64 @sraiw_andi(i32 signext %0, i32 signext %1) nounwind {
 ; RV64-LABEL: sraiw_andi:
 ; RV64:       # %bb.0: # %entry
 ; RV64-NEXT:    add a0, a0, a1
-; RV64-NEXT:    slli a0, a0, 32
-; RV64-NEXT:    srai a0, a0, 2
-; RV64-NEXT:    srli a0, a0, 61
+; RV64-NEXT:    sraiw a0, a0, 31
+; RV64-NEXT:    andi a0, a0, 7
 ; RV64-NEXT:    ret
 entry:
   %3 = add i32 %0, %1

[dtcxzyw]

Can you rebase this patch over cfd13cb?

/home/dtcxzyw/WorkSpace/Projects/compilers/llvm-project/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp: In member function ‘virtual void llvm::RISCVDAGToDAGISel::Select(llvm::SDNode*)’:
/home/dtcxzyw/WorkSpace/Projects/compilers/llvm-project/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp:1465: error: ‘IsC1ANDI’ was not declared in this scope
 1465 |       bool Skip = C2 > 32 && IsC1ANDI && X.getOpcode() == ISD::SHL &&
      | 
ninja: build stopped: subcommand failed.

[dtcxzyw]

LGTM. Thank you!

[llvm-ci]

LLVM Buildbot has detected a new failure on builder llvm-clang-x86_64-expensive-checks-debian running on gribozavr4 while building llvm at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/16/builds/3026

Here is the relevant piece of the build log for the reference:

Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: TableGen/SubtargetFeatureUniqueNames.td' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: not /b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/llvm-tblgen -gen-subtarget -I /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/../../include /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td 2>&1 | /b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/FileCheck /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td -DFILE=/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td
+ not /b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/llvm-tblgen -gen-subtarget -I /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/../../include /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td
+ /b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/FileCheck /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td -DFILE=/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td
/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td:10:11: error: CHECK: expected string not found in input
// CHECK: [[FILE]]:[[@LINE+2]]:5: error: Feature `NameA` already defined.
          ^
<stdin>:1:1: note: scanning from here
/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td:8:5: error: Feature `NameA` already defined.
^
<stdin>:1:1: note: with "FILE" equal to "/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames\\.td"
/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td:8:5: error: Feature `NameA` already defined.
^
<stdin>:1:1: note: with "@LINE+2" equal to "12"
/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td:8:5: error: Feature `NameA` already defined.
^
<stdin>:1:110: note: possible intended match here
/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td:8:5: error: Feature `NameA` already defined.
                                                                                                             ^

Input file: <stdin>
Check file: /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td

-dump-input=help explains the following input dump.

Input was:
<<<<<<
            1: /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td:8:5: error: Feature `NameA` already defined. 
check:10'0     X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
check:10'1                                                                                                                                                                 with "FILE" equal to "/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames\\.td"
check:10'2                                                                                                                                                                 with "@LINE+2" equal to "12"
check:10'3                                                                                                                  ?                                              possible intended match
            2: def FeatureA : SubtargetFeature<"NameA", "", "", "">; 
check:10'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            3:  ^ 
check:10'0     ~~~
            4: /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/SubtargetFeatureUniqueNames.td:12:5: note: Previous definition here. 
check:10'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            5: def FeatureB : SubtargetFeature<"NameA", "", "", "">; 
check:10'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            6:  ^ 
check:10'0     ~~~
>>>>>>

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