Subzero: Fold icmp into br/select lowering.

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) {
+entry:
+  %cmp1 = icmp slt i32 %arg1, %arg2
+  br i1 %cmp1, label %branch1, label %branch2
+branch1:
+  ret i32 1
+branch2:
+  ret i32 2
+}
+
+; CHECK-LABEL: fold_cmp_br
+; CHECK: cmp
+; CHECK: jge
+
+
+; Cmp/branch folding with intervening instructions.
+define i32 @fold_cmp_br_intervening_insts(i32 %arg1, i32 %arg2) {
+entry:
+  %cmp1 = icmp slt i32 %arg1, %arg2
+  call void @use_value(i32 %arg1)
+  br i1 %cmp1, label %branch1, label %branch2
+branch1:
+  ret i32 1
+branch2:
+  ret i32 2
+}
+
+; CHECK-LABEL: fold_cmp_br_intervening_insts
+; CHECK: call
+; CHECK: cmp
+; CHECK: jge
+
+
+; Cmp/branch non-folding because of live-out.
+define i32 @no_fold_cmp_br_liveout(i32 %arg1, i32 %arg2) {
+entry:
+  %cmp1 = icmp slt i32 %arg1, %arg2
+  br label %next
+next:
+  br i1 %cmp1, label %branch1, label %branch2
+branch1:
+  ret i32 1
+branch2:
+  ret i32 2
+}
+
+; CHECK-LABEL: no_fold_cmp_br_liveout
+; CHECK: cmp
+; CHECK: set
+; CHECK: cmp
+; CHECK: je
+
+
+; Cmp/branch non-folding because of extra non-whitelisted uses.
+define i32 @no_fold_cmp_br_non_whitelist(i32 %arg1, i32 %arg2) {
+entry:
+  %cmp1 = icmp slt i32 %arg1, %arg2
+  %result = zext i1 %cmp1 to i32
+  br i1 %cmp1, label %branch1, label %branch2
+branch1:
+  ret i32 %result
+branch2:
+  ret i32 2
+}
+
+; CHECK-LABEL: no_fold_cmp_br_non_whitelist
+; CHECK: cmp
+; CHECK: set
+; CHECK: movzx
+; CHECK: cmp
+; CHECK: je
+
+
+; 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
+
+
+; 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
+
+
+; 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: call

[jvoung (off chromium), 2015/05/15 21:48:20]

Maybe show the ; CHECK-NOT: cmp

before the call, if that's now moved?

[Jim Stichnoth, 2015/05/16 17:32:51]

Done.  (in both "intervening" tests)

+; CHECK: cmp
+; CHECK: jl
+; CHECK: mov
+
+
+; 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: cmp
+; CHECK: jl
+; CHECK: cmp
+; CHECK: jl
+; 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: cmp
+; CHECK: jne
+; CHECK: cmp
+; CHECK: jne
+; 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: cmp
+; CHECK: jne
+; CHECK: cmp
+; CHECK: jne
+; CHECK: movzx
+; CHECK: add
+; CHECK: add
+; CHECK: add