[mips] Fix inefficient code generation.

This patch eliminates the need to emit a constant move instruction when this
pattern is matched:

(select (setgt a, Constant), T, F)

The pattern above effectively turns into this:

(conditional-move (setlt a, Constant + 1), F, T)



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176384 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 140 insertions, 3 deletions

diff --git a/test/CodeGen/Mips/cmov.ll b/test/CodeGen/Mips/cmov.ll
index 3af899a..81925a4 100755
--- a/test/CodeGen/Mips/cmov.ll
+++ b/test/CodeGen/Mips/cmov.ll
@@ -59,3 +59,140 @@ entry:
   ret i64 %cond
 }
 
+; slti and conditional move.
+;
+; Check that, pattern
+;  (select (setgt a, N), t, f)
+; turns into
+;  (movz t, (setlt a, N + 1), f)
+; if N + 1 fits in 16-bit.
+
+; O32: slti0:
+; O32: slti $[[R0:[0-9]+]], ${{[0-9]+}}, 32767
+; O32: movz ${{[0-9]+}}, ${{[0-9]+}}, $[[R0]]
+
+define i32 @slti0(i32 %a) {
+entry:
+  %cmp = icmp sgt i32 %a, 32766
+  %cond = select i1 %cmp, i32 3, i32 4
+  ret i32 %cond
+}
+
+; O32: slti1:
+; O32: slt ${{[0-9]+}}
+
+define i32 @slti1(i32 %a) {
+entry:
+  %cmp = icmp sgt i32 %a, 32767
+  %cond = select i1 %cmp, i32 3, i32 4
+  ret i32 %cond
+}
+
+; O32: slti2:
+; O32: slti $[[R0:[0-9]+]], ${{[0-9]+}}, -32768
+; O32: movz ${{[0-9]+}}, ${{[0-9]+}}, $[[R0]]
+
+define i32 @slti2(i32 %a) {
+entry:
+  %cmp = icmp sgt i32 %a, -32769
+  %cond = select i1 %cmp, i32 3, i32 4
+  ret i32 %cond
+}
+
+; O32: slti3:
+; O32: slt ${{[0-9]+}}
+
+define i32 @slti3(i32 %a) {
+entry:
+  %cmp = icmp sgt i32 %a, -32770
+  %cond = select i1 %cmp, i32 3, i32 4
+  ret i32 %cond
+}
+
+; 64-bit patterns.
+
+; N64: slti64_0:
+; N64: slti $[[R0:[0-9]+]], ${{[0-9]+}}, 32767
+; N64: movz ${{[0-9]+}}, ${{[0-9]+}}, $[[R0]]
+
+define i64 @slti64_0(i64 %a) {
+entry:
+  %cmp = icmp sgt i64 %a, 32766
+  %conv = select i1 %cmp, i64 3, i64 4
+  ret i64 %conv
+}
+
+; N64: slti64_1:
+; N64: slt ${{[0-9]+}}
+
+define i64 @slti64_1(i64 %a) {
+entry:
+  %cmp = icmp sgt i64 %a, 32767
+  %conv = select i1 %cmp, i64 3, i64 4
+  ret i64 %conv
+}
+
+; N64: slti64_2:
+; N64: slti $[[R0:[0-9]+]], ${{[0-9]+}}, -32768
+; N64: movz ${{[0-9]+}}, ${{[0-9]+}}, $[[R0]]
+
+define i64 @slti64_2(i64 %a) {
+entry:
+  %cmp = icmp sgt i64 %a, -32769
+  %conv = select i1 %cmp, i64 3, i64 4
+  ret i64 %conv
+}
+
+; N64: slti64_3:
+; N64: slt ${{[0-9]+}}
+
+define i64 @slti64_3(i64 %a) {
+entry:
+  %cmp = icmp sgt i64 %a, -32770
+  %conv = select i1 %cmp, i64 3, i64 4
+  ret i64 %conv
+}
+
+; sltiu instructions.
+
+; O32: sltiu0:
+; O32: sltiu $[[R0:[0-9]+]], ${{[0-9]+}}, 32767
+; O32: movz ${{[0-9]+}}, ${{[0-9]+}}, $[[R0]]
+
+define i32 @sltiu0(i32 %a) {
+entry:
+  %cmp = icmp ugt i32 %a, 32766
+  %cond = select i1 %cmp, i32 3, i32 4
+  ret i32 %cond
+}
+
+; O32: sltiu1:
+; O32: sltu ${{[0-9]+}}
+
+define i32 @sltiu1(i32 %a) {
+entry:
+  %cmp = icmp ugt i32 %a, 32767
+  %cond = select i1 %cmp, i32 3, i32 4
+  ret i32 %cond
+}
+
+; O32: sltiu2:
+; O32: sltiu $[[R0:[0-9]+]], ${{[0-9]+}}, -32768
+; O32: movz ${{[0-9]+}}, ${{[0-9]+}}, $[[R0]]
+
+define i32 @sltiu2(i32 %a) {
+entry:
+  %cmp = icmp ugt i32 %a, -32769
+  %cond = select i1 %cmp, i32 3, i32 4
+  ret i32 %cond
+}
+
+; O32: sltiu3:
+; O32: sltu ${{[0-9]+}}
+
+define i32 @sltiu3(i32 %a) {
+entry:
+  %cmp = icmp ugt i32 %a, -32770
+  %cond = select i1 %cmp, i32 3, i32 4
+  ret i32 %cond
+}
diff --git a/test/CodeGen/Mips/mips64-f128.ll b/test/CodeGen/Mips/mips64-f128.ll
index 9aa8b8e..c6dd434 100644
--- a/test/CodeGen/Mips/mips64-f128.ll
+++ b/test/CodeGen/Mips/mips64-f128.ll
@@ -632,9 +632,9 @@ entry:
 ; CHECK: or   $[[R3:[0-9]+]], $8, $zero
 ; CHECK: ld   $25, %call16(__gttf2)($gp)
 ; CHECK: jalr $25
-; CHECK: slt  $1, $zero, $2
-; CHECK: movn $[[R1]], $[[R3]], $1
-; CHECK: movn $[[R0]], $[[R2]], $1
+; CHECK: slti $1, $2, 1
+; CHECK: movz $[[R1]], $[[R3]], $1
+; CHECK: movz $[[R0]], $[[R2]], $1
 ; CHECK: or   $2, $[[R1]], $zero
 ; CHECK: or   $3, $[[R0]], $zero