[llvm] [InstCombine][foldPHIArgGEPIntoPHI] Early return for const vector index for gep inst. (PR #138661)

[Nikita Popov via llvm-commits]

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@@ -0,0 +1,35 @@
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+%vec = type { %vec_base }
+%vec_base = type { [4 x float] }
+%foo = type { %vec, %vec}
+
+define void @test(i1 %tobool, ptr addrspace(1) %add.ptr.i) {
+entry:
+  %lane.0 = alloca %foo, align 16
+  %lane.15 = insertelement <16 x ptr> undef, ptr %lane.0, i64 0
+  %mm_vectorGEP = getelementptr inbounds %foo, <16 x ptr> %lane.15, <16 x i64> zeroinitializer, <16 x i32> splat (i32 1), <16 x i32> zeroinitializer, <16 x i32> zeroinitializer, <16 x i64> splat (i64 1)
+  %mm_vectorGEP2 = getelementptr inbounds %foo, <16 x ptr> %lane.15, <16 x i64> zeroinitializer, <16 x i32> zeroinitializer, <16 x i32> zeroinitializer, <16 x i32> zeroinitializer, <16 x i64> splat (i64 1)
+  br i1 %tobool, label %f1, label %f0
+
+f0:
+; CHECK: f0:
+; CHECK-NEXT: %mm_vectorGEP = getelementptr inbounds %foo, <16 x ptr> %lane.15, <16 x i64> zeroinitializer, <16 x i32> splat (i32 1), <16 x i32> zeroinitializer, <16 x i32> zeroinitializer, <16 x i64> splat (i64 1)
+  br label %merge
+
+f1:
+; CHECK: f1:
+; CHECK-NEXT: %mm_vectorGEP2 = getelementptr inbounds %foo, <16 x ptr> %lane.15, <16 x i64> zeroinitializer, <16 x i32> zeroinitializer, <16 x i32> zeroinitializer, <16 x i32> zeroinitializer, <16 x i64> splat (i64 1)
+  br label %merge
+
+merge:
+; CHECK: merge:
+; CHECK-NEXT: %vec.phi14 = phi <16 x ptr> [ %mm_vectorGEP, %f0 ], [ %mm_vectorGEP2, %f1 ]
+  %vec.phi14 = phi <16 x ptr> [ %mm_vectorGEP, %f0], [ %mm_vectorGEP2, %f1 ]
+  %wide.masked.gather15 = call <16 x float> @llvm.masked.gather.v16f32.v16p0(<16 x ptr> %vec.phi14, i32 4, <16 x i1> splat (i1 true), <16 x float> poison)
+  %wide.masked.gather15.extract.15. = extractelement <16 x float> %wide.masked.gather15, i32 15
+  store float %wide.masked.gather15.extract.15., ptr addrspace(1) %add.ptr.i, align 4
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nikic wrote:

Is it possible to further simplify the test? I don't think the masked gather etc is actually needed.

https://github.com/llvm/llvm-project/pull/138661