[NFC][InstCombine] Add preliminary tests for D76983

[dsprenkels]

Summary

This diff adds preliminary tests for the patch submitted in https://reviews.llvm.org/D76983.

I have no commit permissions for LLVM yet; can somebody commit this for me?

[spatel]

LGTM - I'll push this.

llvm/test/Transforms/InstCombine/trunc-extractelement.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S -data-layout="e" | FileCheck %s --check-prefixes=ANY,LE
+; RUN: opt < %s -instcombine -S -data-layout="E" | FileCheck %s --check-prefixes=ANY,BE
+
+define i32 @shrinkExtractElt_i64_to_i32_0(<3 x i64> %x) {
+; ANY-LABEL: @shrinkExtractElt_i64_to_i32_0(
+; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i32 0
+; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i32
+; ANY-NEXT:    ret i32 [[T]]
+;
+  %e = extractelement <3 x i64> %x, i32 0
+  %t = trunc i64 %e to i32
+  ret i32 %t
+}
+
+define i32 @shrinkExtractElt_i64_to_i32_1(<3 x i64> %x) {
+; ANY-LABEL: @shrinkExtractElt_i64_to_i32_1(
+; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i32 1
+; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i32
+; ANY-NEXT:    ret i32 [[T]]
+;
+  %e = extractelement <3 x i64> %x, i32 1
+  %t = trunc i64 %e to i32
+  ret i32 %t
+}
+
+define i32 @shrinkExtractElt_i64_to_i32_2(<3 x i64> %x) {
+; ANY-LABEL: @shrinkExtractElt_i64_to_i32_2(
+; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i32 2
+; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i32
+; ANY-NEXT:    ret i32 [[T]]
+;
+  %e = extractelement <3 x i64> %x, i32 2
+  %t = trunc i64 %e to i32
+  ret i32 %t
+}
+
+define i16 @shrinkExtractElt_i64_to_i16_0(<3 x i64> %x) {
+; ANY-LABEL: @shrinkExtractElt_i64_to_i16_0(
+; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i16 0
+; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i16
+; ANY-NEXT:    ret i16 [[T]]
+;
+  %e = extractelement <3 x i64> %x, i16 0
+  %t = trunc i64 %e to i16
+  ret i16 %t
+}
+
+define i16 @shrinkExtractElt_i64_to_i16_1(<3 x i64> %x) {
+; ANY-LABEL: @shrinkExtractElt_i64_to_i16_1(
+; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i16 1
+; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i16
+; ANY-NEXT:    ret i16 [[T]]
+;
+  %e = extractelement <3 x i64> %x, i16 1
+  %t = trunc i64 %e to i16
+  ret i16 %t
+}
+
+define i16 @shrinkExtractElt_i64_to_i16_2(<3 x i64> %x) {
+; ANY-LABEL: @shrinkExtractElt_i64_to_i16_2(
+; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i16 2
+; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i16
+; ANY-NEXT:    ret i16 [[T]]
+;
+  %e = extractelement <3 x i64> %x, i16 2
+  %t = trunc i64 %e to i16
+  ret i16 %t
+}
+
+; Do not optimize if it would result in an invalid bitcast instruction.
+define i13 @shrinkExtractElt_i67_to_i13_2(<3 x i67> %x) {
+; ANY-LABEL: @shrinkExtractElt_i67_to_i13_2(
+; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i67> [[X:%.*]], i459 2
+; ANY-NEXT:    [[T:%.*]] = trunc i67 [[E]] to i13
+; ANY-NEXT:    ret i13 [[T]]
+;
+  %e = extractelement <3 x i67> %x, i459 2
+  %t = trunc i67 %e to i13
+  ret i13 %t
+}
+
+; Do not optimize if the bitcast instruction would be valid, but the
+; transform would be wrong.
+define i30 @shrinkExtractElt_i40_to_i30_1(<3 x i40> %x) {
+; ANY-LABEL: @shrinkExtractElt_i40_to_i30_1(
+; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i40> [[X:%.*]], i32 1
+; ANY-NEXT:    [[T:%.*]] = trunc i40 [[E]] to i30
+; ANY-NEXT:    ret i30 [[T]]
+;
+  %e = extractelement <3 x i40> %x, i32 1
+  %t = trunc i40 %e to i30
+  ret i30 %t
+}
+
+; Do not canonicalize if that would increase the instruction count.
+declare void @use(i64)
+define i16 @shrinkExtractElt_i64_to_i16_2_extra_use(<3 x i64> %x) {
+; ANY-LABEL: @shrinkExtractElt_i64_to_i16_2_extra_use(
+; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i64 2
+; ANY-NEXT:    call void @use(i64 [[E]])
+; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i16
+; ANY-NEXT:    ret i16 [[T]]
+;
+  %e = extractelement <3 x i64> %x, i64 2
+  call void @use(i64 %e)
+  %t = trunc i64 %e to i16
+  ret i16 %t
+}
+
+; Check to ensure PR45314 remains fixed.
+define <4 x i64> @PR45314(<4 x i64> %x) {
+; ANY-LABEL: @PR45314(
+; ANY-NEXT:    [[E:%.*]] = extractelement <4 x i64> [[X:%.*]], i32 0
+; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i32
+; ANY-NEXT:    [[I:%.*]] = insertelement <8 x i32> undef, i32 [[T]], i32 0
+; ANY-NEXT:    [[S:%.*]] = shufflevector <8 x i32> [[I]], <8 x i32> undef, <8 x i32> zeroinitializer
+; ANY-NEXT:    [[B:%.*]] = bitcast <8 x i32> [[S]] to <4 x i64>
+; ANY-NEXT:    ret <4 x i64> [[B]]
+;
+  %e = extractelement <4 x i64> %x, i32 0
+  %t = trunc i64 %e to i32
+  %i = insertelement <8 x i32> undef, i32 %t, i32 0
+  %s = shufflevector <8 x i32> %i, <8 x i32> undef, <8 x i32> zeroinitializer
+  %b = bitcast <8 x i32> %s to <4 x i64>
+  ret <4 x i64> %b
+}