[InstCombine] add folds for icmp (smin X, Y), X

Min/max canonicalization (r287585) exposes the fact that we're missing combines for min/max patterns. 
This patch won't solve the example that was attached to that thread, so something else still needs fixing.

The line between InstCombine and InstSimplify gets blurry here because sometimes the icmp instruction that
we want to fold to already exists, but sometimes it's the swapped form of what we want.

Corresponding changes for smax/umin/umax to follow.

Differential Revision: https://reviews.llvm.org/D27531

llvm-svn: 289855

1 files changed, 12 insertions, 36 deletions

diff --git a/llvm/test/Transforms/InstCombine/smin-icmp.ll b/llvm/test/Transforms/InstCombine/smin-icmp.ll
index 083d0639026..b3e375fdcdd 100644
--- a/llvm/test/Transforms/InstCombine/smin-icmp.ll
+++ b/llvm/test/Transforms/InstCombine/smin-icmp.ll
@@ -11,9 +11,7 @@
 
 define i1 @eq_smin1(i32 %x, i32 %y) {
 ; CHECK-LABEL: @eq_smin1(
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 %x, %y
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp eq i32 [[SEL]], %x
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sle i32 %x, %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %cmp1 = icmp slt i32 %x, %y
@@ -26,9 +24,7 @@ define i1 @eq_smin1(i32 %x, i32 %y) {
 
 define i1 @eq_smin2(i32 %x, i32 %y) {
 ; CHECK-LABEL: @eq_smin2(
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 %y, %x
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 %x
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp eq i32 [[SEL]], %x
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sle i32 %x, %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %cmp1 = icmp slt i32 %y, %x
@@ -42,9 +38,7 @@ define i1 @eq_smin2(i32 %x, i32 %y) {
 define i1 @eq_smin3(i32 %a, i32 %y) {
 ; CHECK-LABEL: @eq_smin3(
 ; CHECK-NEXT:    [[X:%.*]] = add i32 %a, 3
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 [[X]], %y
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp eq i32 [[X]], [[SEL]]
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sle i32 [[X]], %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %x = add i32 %a, 3 ; thwart complexity-based canonicalization
@@ -59,9 +53,7 @@ define i1 @eq_smin3(i32 %a, i32 %y) {
 define i1 @eq_smin4(i32 %a, i32 %y) {
 ; CHECK-LABEL: @eq_smin4(
 ; CHECK-NEXT:    [[X:%.*]] = add i32 %a, 3
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp sgt i32 [[X]], %y
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 [[X]]
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp eq i32 [[X]], [[SEL]]
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sle i32 [[X]], %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %x = add i32 %a, 3 ; thwart complexity-based canonicalization
@@ -75,9 +67,7 @@ define i1 @eq_smin4(i32 %a, i32 %y) {
 
 define i1 @sge_smin1(i32 %x, i32 %y) {
 ; CHECK-LABEL: @sge_smin1(
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 %x, %y
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp sge i32 [[SEL]], %x
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sle i32 %x, %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %cmp1 = icmp slt i32 %x, %y
@@ -90,9 +80,7 @@ define i1 @sge_smin1(i32 %x, i32 %y) {
 
 define i1 @sge_smin2(i32 %x, i32 %y) {
 ; CHECK-LABEL: @sge_smin2(
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 %y, %x
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 %x
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp sge i32 [[SEL]], %x
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sle i32 %x, %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %cmp1 = icmp slt i32 %y, %x
@@ -106,9 +94,7 @@ define i1 @sge_smin2(i32 %x, i32 %y) {
 define i1 @sge_smin3(i32 %a, i32 %y) {
 ; CHECK-LABEL: @sge_smin3(
 ; CHECK-NEXT:    [[X:%.*]] = add i32 %a, 3
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 [[X]], %y
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp sle i32 [[X]], [[SEL]]
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sle i32 [[X]], %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %x = add i32 %a, 3 ; thwart complexity-based canonicalization
@@ -123,9 +109,7 @@ define i1 @sge_smin3(i32 %a, i32 %y) {
 define i1 @sge_smin4(i32 %a, i32 %y) {
 ; CHECK-LABEL: @sge_smin4(
 ; CHECK-NEXT:    [[X:%.*]] = add i32 %a, 3
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp sgt i32 [[X]], %y
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 [[X]]
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp sle i32 [[X]], [[SEL]]
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sle i32 [[X]], %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %x = add i32 %a, 3 ; thwart complexity-based canonicalization
@@ -139,9 +123,7 @@ define i1 @sge_smin4(i32 %a, i32 %y) {
 
 define i1 @ne_smin1(i32 %x, i32 %y) {
 ; CHECK-LABEL: @ne_smin1(
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 %x, %y
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp ne i32 [[SEL]], %x
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sgt i32 %x, %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %cmp1 = icmp slt i32 %x, %y
@@ -168,9 +150,7 @@ define i1 @ne_smin2(i32 %x, i32 %y) {
 define i1 @ne_smin3(i32 %a, i32 %y) {
 ; CHECK-LABEL: @ne_smin3(
 ; CHECK-NEXT:    [[X:%.*]] = add i32 %a, 3
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 [[X]], %y
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp ne i32 [[X]], [[SEL]]
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sgt i32 [[X]], %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %x = add i32 %a, 3 ; thwart complexity-based canonicalization
@@ -199,9 +179,7 @@ define i1 @ne_smin4(i32 %a, i32 %y) {
 
 define i1 @slt_smin1(i32 %x, i32 %y) {
 ; CHECK-LABEL: @slt_smin1(
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 %x, %y
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp slt i32 [[SEL]], %x
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sgt i32 %x, %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %cmp1 = icmp slt i32 %x, %y
@@ -228,9 +206,7 @@ define i1 @slt_smin2(i32 %x, i32 %y) {
 define i1 @slt_smin3(i32 %a, i32 %y) {
 ; CHECK-LABEL: @slt_smin3(
 ; CHECK-NEXT:    [[X:%.*]] = add i32 %a, 3
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 [[X]], %y
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp sgt i32 [[X]], [[SEL]]
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sgt i32 [[X]], %y
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
   %x = add i32 %a, 3 ; thwart complexity-based canonicalization