Subzero: Use cmov to improve lowering for the select instruction.

tests_lit/llvm2ice_tests/bool-folding.ll

 ; This tests the optimization where producers and consumers of i1 (bool)
 ; variables are combined to implicitly use flags instead of explicitly using
 ; stack or register variables.
 
 ; RUN: %p2i -i %s --filetype=obj --disassemble --args -O2 | FileCheck %s
 
 declare void @use_value(i32)
 
 ; Basic cmp/branch folding.
 define i32 @fold_cmp_br(i32 %arg1, i32 %arg2) {
@@ skipping 73 matching lines @@
 ; Basic cmp/select folding.
 define i32 @fold_cmp_select(i32 %arg1, i32 %arg2) {
 entry:
   %cmp1 = icmp slt i32 %arg1, %arg2
   %result = select i1 %cmp1, i32 %arg1, i32 %arg2
   ret i32 %result
 }
 
 ; CHECK-LABEL: fold_cmp_select
 ; CHECK: cmp
-; CHECK: jl
-; CHECK: mov
+; CHECK: cmovl
 
 
 ; 64-bit cmp/select folding.
 define i64 @fold_cmp_select_64(i64 %arg1, i64 %arg2) {
 entry:
   %arg1_trunc = trunc i64 %arg1 to i32
   %arg2_trunc = trunc i64 %arg2 to i32
   %cmp1 = icmp slt i32 %arg1_trunc, %arg2_trunc
   %result = select i1 %cmp1, i64 %arg1, i64 %arg2
   ret i64 %result
 }
 
 ; CHECK-LABEL: fold_cmp_select_64
 ; CHECK: cmp
-; CHECK: jl
-; CHECK: mov
-; CHECK: mov
+; CHECK: cmovl
+; CHECK: cmovl
 
 
 ; Cmp/select folding with intervening instructions.
 define i32 @fold_cmp_select_intervening_insts(i32 %arg1, i32 %arg2) {
 entry:
   %cmp1 = icmp slt i32 %arg1, %arg2
   call void @use_value(i32 %arg1)
   %result = select i1 %cmp1, i32 %arg1, i32 %arg2
   ret i32 %result
 }
 
 ; CHECK-LABEL: fold_cmp_select_intervening_insts
 ; CHECK-NOT: cmp
 ; CHECK: call
 ; CHECK: cmp
-; CHECK: jl
-; CHECK: mov
+; CHECK: cmovl
 
 
 ; Cmp/multi-select folding.
 define i32 @fold_cmp_select_multi(i32 %arg1, i32 %arg2) {
 entry:
   %cmp1 = icmp slt i32 %arg1, %arg2
   %a = select i1 %cmp1, i32 %arg1, i32 %arg2
   %b = select i1 %cmp1, i32 %arg2, i32 %arg1
   %c = select i1 %cmp1, i32 123, i32 %arg1
   %partial = add i32 %a, %b
   %result = add i32 %partial, %c
   ret i32 %result
 }
 
 ; CHECK-LABEL: fold_cmp_select_multi
 ; CHECK: cmp
-; CHECK: jl
+; CHECK: cmovl
 ; CHECK: cmp
-; CHECK: jl
+; CHECK: cmovl
 ; CHECK: cmp
-; CHECK: jl
+; CHECK: cmovge
 ; CHECK: add
 ; CHECK: add
 
 
 ; Cmp/multi-select non-folding because of live-out.
 define i32 @no_fold_cmp_select_multi_liveout(i32 %arg1, i32 %arg2) {
 entry:
   %cmp1 = icmp slt i32 %arg1, %arg2
   %a = select i1 %cmp1, i32 %arg1, i32 %arg2
   %b = select i1 %cmp1, i32 %arg2, i32 %arg1
   br label %next
 next:
   %c = select i1 %cmp1, i32 123, i32 %arg1
   %partial = add i32 %a, %b
   %result = add i32 %partial, %c
   ret i32 %result
 }
 
 ; CHECK-LABEL: no_fold_cmp_select_multi_liveout
 ; CHECK: set
 ; CHECK: cmp
-; CHECK: jne
+; CHECK: cmovne
 ; CHECK: cmp
-; CHECK: jne
+; CHECK: cmovne
 ; CHECK: cmp
-; CHECK: jne
+; CHECK: cmove
 ; CHECK: add
 ; CHECK: add
 
 
 ; Cmp/multi-select non-folding because of extra non-whitelisted uses.
 define i32 @no_fold_cmp_select_multi_non_whitelist(i32 %arg1, i32 %arg2) {
 entry:
   %cmp1 = icmp slt i32 %arg1, %arg2
   %a = select i1 %cmp1, i32 %arg1, i32 %arg2
   %b = select i1 %cmp1, i32 %arg2, i32 %arg1
   %c = select i1 %cmp1, i32 123, i32 %arg1
   %ext = zext i1 %cmp1 to i32
   %partial1 = add i32 %a, %b
   %partial2 = add i32 %partial1, %c
   %result = add i32 %partial2, %ext
   ret i32 %result
 }
 
 ; CHECK-LABEL: no_fold_cmp_select_multi_non_whitelist
 ; CHECK: set
 ; CHECK: cmp
-; CHECK: jne
+; CHECK: cmovne
 ; CHECK: cmp
-; CHECK: jne
+; CHECK: cmovne
 ; CHECK: cmp
-; CHECK: jne
+; CHECK: cmove
 ; CHECK: movzx
 ; CHECK: add
 ; CHECK: add
 ; CHECK: add