[NFC][InstCombine] conditional sign-extend of high-bit-extract: 'and' pat. can be 'or' pattern.

In this pattern, all the "magic" bits that we'd add are all
high sign bits, and in the value we'd be adding to they are all unset,
not unexpectedly, so we can have an `or` there:
https://rise4fun.com/Alive/ups

llvm-svn: 375377

Author: LebedevRI

llvm/test/Transforms/InstCombine/conditional-variable-length-signext-after-high-bit-extract.ll

@@ -45,6 +45,37 @@ define i32 @t0_notrunc_add(i32 %data, i32 %nbits) {
   ret i32 %signextended
 }
 
+define i32 @t0_notrunc_or(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @t0_notrunc_or(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = or i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = or i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}
+
 define i32 @t1_notrunc_sub(i32 %data, i32 %nbits) {
 ; CHECK-LABEL: @t1_notrunc_sub(
 ; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
@@ -113,6 +144,43 @@ define i32 @t2_trunc_add(i64 %data, i32 %nbits) {
   ret i32 %signextended
 }
 
+define i32 @t2_trunc_or(i64 %data, i32 %nbits) {
+; CHECK-LABEL: @t2_trunc_or(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 64, [[NBITS:%.*]]
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP_WIDE:%.*]] = zext i32 [[LOW_BITS_TO_SKIP]] to i64
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED_WIDE:%.*]] = lshr i64 [[DATA:%.*]], [[LOW_BITS_TO_SKIP_WIDE]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = trunc i64 [[HIGH_BITS_EXTRACTED_WIDE]] to i32
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i64 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 -1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use64(i64 [[LOW_BITS_TO_SKIP_WIDE]])
+; CHECK-NEXT:    call void @use64(i64 [[HIGH_BITS_EXTRACTED_WIDE]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = or i32 [[MAGIC]], [[HIGH_BITS_EXTRACTED]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 64, %nbits
+  %low_bits_to_skip_wide = zext i32 %low_bits_to_skip to i64
+  %high_bits_extracted_wide = lshr i64 %data, %low_bits_to_skip_wide
+  %high_bits_extracted = trunc i64 %high_bits_extracted_wide to i32
+  %should_signext = icmp slt i64 %data, 0
+  %all_bits_except_low_nbits = shl i32 -1, %nbits
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0 ; one-use
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use64(i64 %low_bits_to_skip_wide)
+  call void @use64(i64 %high_bits_extracted_wide)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+
+  %signextended = or i32 %magic, %high_bits_extracted
+  ret i32 %signextended
+}
+
 define i32 @t3_trunc_sub(i64 %data, i32 %nbits) {
 ; CHECK-LABEL: @t3_trunc_sub(
 ; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 64, [[NBITS:%.*]]
@@ -1038,3 +1106,34 @@ define i32 @n28_sub_sext_of_magic(i32 %data, i8 %nbits) {
   %signextended = sub i32 %high_bits_extracted, %magic_wide
   ret i32 %signextended
 }
+
+define i32 @n290_or_with_wrong_magic(i32 %data, i32 %nbits) {
+; CHECK-LABEL: @n290_or_with_wrong_magic(
+; CHECK-NEXT:    [[LOW_BITS_TO_SKIP:%.*]] = sub i32 32, [[NBITS:%.*]]
+; CHECK-NEXT:    [[HIGH_BITS_EXTRACTED:%.*]] = lshr i32 [[DATA:%.*]], [[LOW_BITS_TO_SKIP]]
+; CHECK-NEXT:    [[SHOULD_SIGNEXT:%.*]] = icmp slt i32 [[DATA]], 0
+; CHECK-NEXT:    [[ALL_BITS_EXCEPT_LOW_NBITS:%.*]] = shl i32 1, [[NBITS]]
+; CHECK-NEXT:    [[MAGIC:%.*]] = select i1 [[SHOULD_SIGNEXT]], i32 [[ALL_BITS_EXCEPT_LOW_NBITS]], i32 0
+; CHECK-NEXT:    call void @use32(i32 [[LOW_BITS_TO_SKIP]])
+; CHECK-NEXT:    call void @use32(i32 [[HIGH_BITS_EXTRACTED]])
+; CHECK-NEXT:    call void @use1(i1 [[SHOULD_SIGNEXT]])
+; CHECK-NEXT:    call void @use32(i32 [[ALL_BITS_EXCEPT_LOW_NBITS]])
+; CHECK-NEXT:    call void @use32(i32 [[MAGIC]])
+; CHECK-NEXT:    [[SIGNEXTENDED:%.*]] = or i32 [[HIGH_BITS_EXTRACTED]], [[MAGIC]]
+; CHECK-NEXT:    ret i32 [[SIGNEXTENDED]]
+;
+  %low_bits_to_skip = sub i32 32, %nbits
+  %high_bits_extracted = lshr i32 %data, %low_bits_to_skip
+  %should_signext = icmp slt i32 %data, 0
+  %all_bits_except_low_nbits = shl i32 1, %nbits ; not -1
+  %magic = select i1 %should_signext, i32 %all_bits_except_low_nbits, i32 0
+
+  call void @use32(i32 %low_bits_to_skip)
+  call void @use32(i32 %high_bits_extracted)
+  call void @use1(i1 %should_signext)
+  call void @use32(i32 %all_bits_except_low_nbits)
+  call void @use32(i32 %magic)
+
+  %signextended = or i32 %high_bits_extracted, %magic
+  ret i32 %signextended
+}