[X86] SimplifyDemandedVectorEltsForTargetNode - add X86ISD::MOVDDUP handling

[RKSimon]

Reduce YMM MOVDDUP node to XMM if the upper elements are not demanded

Noticed while working on #140234

[llvmbot]

@llvm/pr-subscribers-backend-x86

Author: Simon Pilgrim (RKSimon)

Changes

Reduce YMM MOVDDUP node to XMM if the upper elements are not demanded

Noticed while working on #140234

---

Full diff: https://github.com/llvm/llvm-project/pull/140237.diff

2 Files Affected:

• (modified) llvm/lib/Target/X86/X86ISelLowering.cpp (+2)
• (modified) llvm/test/CodeGen/X86/vector-shuffle-256-v4.ll (+1-2)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 9be3b39ce16fa..bde4f70b2147f 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -44013,6 +44013,8 @@ bool X86TargetLowering::SimplifyDemandedVectorEltsForTargetNode(
     case X86ISD::VZEXT_MOVL:
       // Variable blend.
     case X86ISD::BLENDV:
+      // Target unary shuffles:
+    case X86ISD::MOVDDUP:
       // Target unary shuffles by immediate:
     case X86ISD::PSHUFD:
     case X86ISD::PSHUFLW:
diff --git a/llvm/test/CodeGen/X86/vector-shuffle-256-v4.ll b/llvm/test/CodeGen/X86/vector-shuffle-256-v4.ll
index cf546dc2671f2..d848a8b879215 100644
--- a/llvm/test/CodeGen/X86/vector-shuffle-256-v4.ll
+++ b/llvm/test/CodeGen/X86/vector-shuffle-256-v4.ll
@@ -861,8 +861,7 @@ define <4 x double> @shuffle_v4f64_2345_0567_select(<4 x double> %vec1, <4 x dou
 define <4 x double> @shuffle_v4f64_1436_split_load(ptr %px, ptr %py) {
 ; AVX1-LABEL: shuffle_v4f64_1436_split_load:
 ; AVX1:       # %bb.0:
-; AVX1-NEXT:    vmovapd (%rsi), %xmm0
-; AVX1-NEXT:    vmovddup {{.*#+}} ymm0 = ymm0[0,0,2,2]
+; AVX1-NEXT:    vmovddup {{.*#+}} xmm0 = mem[0,0]
 ; AVX1-NEXT:    vmovupd (%rdi), %ymm1
 ; AVX1-NEXT:    vinsertf128 $1, 16(%rsi), %ymm0, %ymm0
 ; AVX1-NEXT:    vshufpd {{.*#+}} ymm0 = ymm1[1],ymm0[1],ymm1[3],ymm0[2]

[llvm-ci]

LLVM Buildbot has detected a new failure on builder llvm-clang-x86_64-sie-ubuntu-fast running on sie-linux-worker while building llvm at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/144/builds/25322

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

Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: Analysis/ftime-trace.cpp' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/clang -cc1 -internal-isystem /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/lib/clang/21/include -nostdsysteminc -analyze -analyzer-constraints=range -setup-static-analyzer -analyzer-checker=core /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/ftime-trace.cpp -ftime-trace=/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/test/Analysis/Output/ftime-trace.cpp.tmp.raw.json -ftime-trace-granularity=0 -verify # RUN: at line 1
+ /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/clang -cc1 -internal-isystem /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/lib/clang/21/include -nostdsysteminc -analyze -analyzer-constraints=range -setup-static-analyzer -analyzer-checker=core /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/ftime-trace.cpp -ftime-trace=/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/test/Analysis/Output/ftime-trace.cpp.tmp.raw.json -ftime-trace-granularity=0 -verify
"/usr/bin/python3.10" -c 'import json, sys; print(json.dumps(json.load(sys.stdin), indent=4))' < /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/test/Analysis/Output/ftime-trace.cpp.tmp.raw.json > /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/test/Analysis/Output/ftime-trace.cpp.tmp.formatted.json # RUN: at line 2
+ /usr/bin/python3.10 -c 'import json, sys; print(json.dumps(json.load(sys.stdin), indent=4))'
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/FileCheck --input-file=/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/test/Analysis/Output/ftime-trace.cpp.tmp.formatted.json --check-prefix=CHECK /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/ftime-trace.cpp # RUN: at line 3
+ /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/FileCheck --input-file=/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/test/Analysis/Output/ftime-trace.cpp.tmp.formatted.json --check-prefix=CHECK /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/ftime-trace.cpp
�[1m/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/ftime-trace.cpp:34:11: �[0m�[0;1;31merror: �[0m�[1mCHECK: expected string not found in input
�[0m// CHECK: "name": "Total CheckerManager::runCheckersForStmt (Pre)",
�[0;1;32m          ^
�[0m�[1m/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/test/Analysis/Output/ftime-trace.cpp.tmp.formatted.json:2474:3: �[0m�[0;1;30mnote: �[0m�[1mscanning from here
�[0m }
�[0;1;32m  ^
�[0m�[1m/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/test/Analysis/Output/ftime-trace.cpp.tmp.formatted.json:2674:2: �[0m�[0;1;30mnote: �[0m�[1mpossible intended match here
�[0m "name": "Total CheckerManager::runCheckersForStmt (Post)",
�[0;1;32m ^
�[0m
Input file: /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/tools/clang/test/Analysis/Output/ftime-trace.cpp.tmp.formatted.json
Check file: /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/ftime-trace.cpp

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

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