[InstCombine] add tests for FP<->int casts; NFC

This overlaps with at least some existing tests,
but the smaller types should be faster for alive2
to verify. We know that at least one of these is
currently wrong (miscompile) as shown in #55150.

Author: rotateright

llvm/test/Transforms/InstCombine/sitofp.ll

@@ -245,3 +245,85 @@ define i25 @low_masked_input(i25 %A) {
   %C = fptoui float %B to i25
   ret i25 %C
 }
+
+define i11 @s32_half_s11(i32 %x) {
+; CHECK-LABEL: @s32_half_s11(
+; CHECK-NEXT:    [[R:%.*]] = trunc i32 [[X:%.*]] to i11
+; CHECK-NEXT:    ret i11 [[R]]
+;
+  %h = sitofp i32 %x to half
+  %r = fptosi half %h to i11
+  ret i11 %r
+}
+
+define i11 @s32_half_u11(i32 %x) {
+; CHECK-LABEL: @s32_half_u11(
+; CHECK-NEXT:    [[R:%.*]] = trunc i32 [[X:%.*]] to i11
+; CHECK-NEXT:    ret i11 [[R]]
+;
+  %h = sitofp i32 %x to half
+  %r = fptoui half %h to i11
+  ret i11 %r
+}
+
+define i11 @u32_half_s11(i32 %x) {
+; CHECK-LABEL: @u32_half_s11(
+; CHECK-NEXT:    [[R:%.*]] = trunc i32 [[X:%.*]] to i11
+; CHECK-NEXT:    ret i11 [[R]]
+;
+  %h = uitofp i32 %x to half
+  %r = fptosi half %h to i11
+  ret i11 %r
+}
+
+define i11 @u32_half_u11(i32 %x) {
+; CHECK-LABEL: @u32_half_u11(
+; CHECK-NEXT:    [[R:%.*]] = trunc i32 [[X:%.*]] to i11
+; CHECK-NEXT:    ret i11 [[R]]
+;
+  %h = uitofp i32 %x to half
+  %r = fptoui half %h to i11
+  ret i11 %r
+}
+
+define i12 @s32_half_s12(i32 %x) {
+; CHECK-LABEL: @s32_half_s12(
+; CHECK-NEXT:    [[R:%.*]] = trunc i32 [[X:%.*]] to i12
+; CHECK-NEXT:    ret i12 [[R]]
+;
+  %h = sitofp i32 %x to half
+  %r = fptosi half %h to i12
+  ret i12 %r
+}
+
+define i12 @s32_half_u12(i32 %x) {
+; CHECK-LABEL: @s32_half_u12(
+; CHECK-NEXT:    [[H:%.*]] = sitofp i32 [[X:%.*]] to half
+; CHECK-NEXT:    [[R:%.*]] = fptoui half [[H]] to i12
+; CHECK-NEXT:    ret i12 [[R]]
+;
+  %h = sitofp i32 %x to half
+  %r = fptoui half %h to i12
+  ret i12 %r
+}
+
+define i12 @u32_half_s12(i32 %x) {
+; CHECK-LABEL: @u32_half_s12(
+; CHECK-NEXT:    [[R:%.*]] = trunc i32 [[X:%.*]] to i12
+; CHECK-NEXT:    ret i12 [[R]]
+;
+  %h = uitofp i32 %x to half
+  %r = fptosi half %h to i12
+  ret i12 %r
+}
+
+define i12 @u32_half_u12(i32 %x) {
+; CHECK-LABEL: @u32_half_u12(
+; CHECK-NEXT:    [[H:%.*]] = uitofp i32 [[X:%.*]] to half
+; CHECK-NEXT:    [[R:%.*]] = fptoui half [[H]] to i12
+; CHECK-NEXT:    ret i12 [[R]]
+;
+  %h = uitofp i32 %x to half
+  %r = fptoui half %h to i12
+  ret i12 %r
+}