IR: add "cmpxchg weak" variant to support permitted failure.

This commit adds a weak variant of the cmpxchg operation, as described
in C++11. A cmpxchg instruction with this modifier is permitted to
fail to store, even if the comparison indicated it should.

As a result, cmpxchg instructions must return a flag indicating
success in addition to their original iN value loaded. Thus, for
uniformity *all* cmpxchg instructions now return "{ iN, i1 }". The
second flag is 1 when the store succeeded.

At the DAG level, a new ATOMIC_CMP_SWAP_WITH_SUCCESS node has been
added as the natural representation for the new cmpxchg instructions.
It is a strong cmpxchg.

By default this gets Expanded to the existing ATOMIC_CMP_SWAP during
Legalization, so existing backends should see no change in behaviour.
If they wish to deal with the enhanced node instead, they can call
setOperationAction on it. Beware: as a node with 2 results, it cannot
be selected from TableGen.

Currently, no use is made of the extra information provided in this
patch. Test updates are almost entirely adapting the input IR to the
new scheme.

Summary for out of tree users:
------------------------------

+ Legacy Bitcode files are upgraded during read.
+ Legacy assembly IR files will be invalid.
+ Front-ends must adapt to different type for "cmpxchg".
+ Backends should be unaffected by default.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210903 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 50 insertions, 25 deletions

diff --git a/test/CodeGen/SystemZ/cmpxchg-01.ll b/test/CodeGen/SystemZ/cmpxchg-01.ll
index bb0b18ad57..5118aadcf2 100644
--- a/test/CodeGen/SystemZ/cmpxchg-01.ll
+++ b/test/CodeGen/SystemZ/cmpxchg-01.ll
@@ -32,7 +32,8 @@ define i8 @f1(i8 %dummy, i8 *%src, i8 %cmp, i8 %swap) {
 ; CHECK-SHIFT: lcr [[NEGSHIFT:%r[1-9]+]], [[SHIFT]]
 ; CHECK-SHIFT: rll
 ; CHECK-SHIFT: rll {{%r[0-9]+}}, %r5, -8([[NEGSHIFT]])
-  %res = cmpxchg i8 *%src, i8 %cmp, i8 %swap seq_cst seq_cst
+  %pair = cmpxchg i8 *%src, i8 %cmp, i8 %swap seq_cst seq_cst
+  %res = extractvalue { i8, i1 } %pair, 0
   ret i8 %res
 }
 
@@ -50,6 +51,7 @@ define i8 @f2(i8 *%src) {
 ; CHECK-SHIFT: risbg
 ; CHECK-SHIFT: risbg [[SWAP]], {{%r[0-9]+}}, 32, 55, 0
 ; CHECK-SHIFT: br %r14
-  %res = cmpxchg i8 *%src, i8 42, i8 88 seq_cst seq_cst
+  %pair = cmpxchg i8 *%src, i8 42, i8 88 seq_cst seq_cst
+  %res = extractvalue { i8, i1 } %pair, 0
   ret i8 %res
 }
diff --git a/test/CodeGen/SystemZ/cmpxchg-02.ll b/test/CodeGen/SystemZ/cmpxchg-02.ll
index 8d46a8c073..9eb0628b5a 100644
--- a/test/CodeGen/SystemZ/cmpxchg-02.ll
+++ b/test/CodeGen/SystemZ/cmpxchg-02.ll
@@ -32,7 +32,8 @@ define i16 @f1(i16 %dummy, i16 *%src, i16 %cmp, i16 %swap) {
 ; CHECK-SHIFT: lcr [[NEGSHIFT:%r[1-9]+]], [[SHIFT]]
 ; CHECK-SHIFT: rll
 ; CHECK-SHIFT: rll {{%r[0-9]+}}, %r5, -16([[NEGSHIFT]])
-  %res = cmpxchg i16 *%src, i16 %cmp, i16 %swap seq_cst seq_cst
+  %pair = cmpxchg i16 *%src, i16 %cmp, i16 %swap seq_cst seq_cst
+  %res = extractvalue { i16, i1 } %pair, 0
   ret i16 %res
 }
 
@@ -50,6 +51,7 @@ define i16 @f2(i16 *%src) {
 ; CHECK-SHIFT: risbg
 ; CHECK-SHIFT: risbg [[SWAP]], {{%r[0-9]+}}, 32, 47, 0
 ; CHECK-SHIFT: br %r14
-  %res = cmpxchg i16 *%src, i16 42, i16 88 seq_cst seq_cst
+  %pair = cmpxchg i16 *%src, i16 42, i16 88 seq_cst seq_cst
+  %res = extractvalue { i16, i1 } %pair, 0
   ret i16 %res
 }
diff --git a/test/CodeGen/SystemZ/cmpxchg-03.ll b/test/CodeGen/SystemZ/cmpxchg-03.ll
index f6a2ad0b69..c5fab4dc04 100644
--- a/test/CodeGen/SystemZ/cmpxchg-03.ll
+++ b/test/CodeGen/SystemZ/cmpxchg-03.ll
@@ -7,7 +7,8 @@ define i32 @f1(i32 %cmp, i32 %swap, i32 *%src) {
 ; CHECK-LABEL: f1:
 ; CHECK: cs %r2, %r3, 0(%r4)
 ; CHECK: br %r14
-  %val = cmpxchg i32 *%src, i32 %cmp, i32 %swap seq_cst seq_cst
+  %pair = cmpxchg i32 *%src, i32 %cmp, i32 %swap seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
 
@@ -17,7 +18,8 @@ define i32 @f2(i32 %cmp, i32 %swap, i32 *%src) {
 ; CHECK: cs %r2, %r3, 4092(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i32 *%src, i64 1023
-  %val = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %pair = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
 
@@ -27,7 +29,8 @@ define i32 @f3(i32 %cmp, i32 %swap, i32 *%src) {
 ; CHECK: csy %r2, %r3, 4096(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i32 *%src, i64 1024
-  %val = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %pair = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
 
@@ -37,7 +40,8 @@ define i32 @f4(i32 %cmp, i32 %swap, i32 *%src) {
 ; CHECK: csy %r2, %r3, 524284(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i32 *%src, i64 131071
-  %val = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %pair = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
 
@@ -49,7 +53,8 @@ define i32 @f5(i32 %cmp, i32 %swap, i32 *%src) {
 ; CHECK: cs %r2, %r3, 0(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i32 *%src, i64 131072
-  %val = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %pair = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
 
@@ -59,7 +64,8 @@ define i32 @f6(i32 %cmp, i32 %swap, i32 *%src) {
 ; CHECK: csy %r2, %r3, -4(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i32 *%src, i64 -1
-  %val = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %pair = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
 
@@ -69,7 +75,8 @@ define i32 @f7(i32 %cmp, i32 %swap, i32 *%src) {
 ; CHECK: csy %r2, %r3, -524288(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i32 *%src, i64 -131072
-  %val = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %pair = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
 
@@ -81,7 +88,8 @@ define i32 @f8(i32 %cmp, i32 %swap, i32 *%src) {
 ; CHECK: cs %r2, %r3, 0(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i32 *%src, i64 -131073
-  %val = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %pair = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
 
@@ -93,7 +101,8 @@ define i32 @f9(i32 %cmp, i32 %swap, i64 %src, i64 %index) {
 ; CHECK: br %r14
   %add1 = add i64 %src, %index
   %ptr = inttoptr i64 %add1 to i32 *
-  %val = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %pair = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
 
@@ -106,7 +115,8 @@ define i32 @f10(i32 %cmp, i32 %swap, i64 %src, i64 %index) {
   %add1 = add i64 %src, %index
   %add2 = add i64 %add1, 4096
   %ptr = inttoptr i64 %add2 to i32 *
-  %val = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %pair = cmpxchg i32 *%ptr, i32 %cmp, i32 %swap seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
 
@@ -116,7 +126,8 @@ define i32 @f11(i32 %dummy, i32 %swap, i32 *%ptr) {
 ; CHECK: lhi %r2, 1001
 ; CHECK: cs %r2, %r3, 0(%r4)
 ; CHECK: br %r14
-  %val = cmpxchg i32 *%ptr, i32 1001, i32 %swap seq_cst seq_cst
+  %pair = cmpxchg i32 *%ptr, i32 1001, i32 %swap seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
 
@@ -126,6 +137,7 @@ define i32 @f12(i32 %cmp, i32 *%ptr) {
 ; CHECK: lhi [[SWAP:%r[0-9]+]], 1002
 ; CHECK: cs %r2, [[SWAP]], 0(%r3)
 ; CHECK: br %r14
-  %val = cmpxchg i32 *%ptr, i32 %cmp, i32 1002 seq_cst seq_cst
+  %pair = cmpxchg i32 *%ptr, i32 %cmp, i32 1002 seq_cst seq_cst
+  %val = extractvalue { i32, i1 } %pair, 0
   ret i32 %val
 }
diff --git a/test/CodeGen/SystemZ/cmpxchg-04.ll b/test/CodeGen/SystemZ/cmpxchg-04.ll
index 069bad6514..ba1493e185 100644
--- a/test/CodeGen/SystemZ/cmpxchg-04.ll
+++ b/test/CodeGen/SystemZ/cmpxchg-04.ll
@@ -7,7 +7,8 @@ define i64 @f1(i64 %cmp, i64 %swap, i64 *%src) {
 ; CHECK-LABEL: f1:
 ; CHECK: csg %r2, %r3, 0(%r4)
 ; CHECK: br %r14
-  %val = cmpxchg i64 *%src, i64 %cmp, i64 %swap seq_cst seq_cst
+  %pairval = cmpxchg i64 *%src, i64 %cmp, i64 %swap seq_cst seq_cst
+  %val = extractvalue { i64, i1 } %pairval, 0
   ret i64 %val
 }
 
@@ -17,7 +18,8 @@ define i64 @f2(i64 %cmp, i64 %swap, i64 *%src) {
 ; CHECK: csg %r2, %r3, 524280(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i64 *%src, i64 65535
-  %val = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %pairval = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %val = extractvalue { i64, i1 } %pairval, 0
   ret i64 %val
 }
 
@@ -29,7 +31,8 @@ define i64 @f3(i64 %cmp, i64 %swap, i64 *%src) {
 ; CHECK: csg %r2, %r3, 0(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i64 *%src, i64 65536
-  %val = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %pairval = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %val = extractvalue { i64, i1 } %pairval, 0
   ret i64 %val
 }
 
@@ -39,7 +42,8 @@ define i64 @f4(i64 %cmp, i64 %swap, i64 *%src) {
 ; CHECK: csg %r2, %r3, -8(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i64 *%src, i64 -1
-  %val = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %pairval = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %val = extractvalue { i64, i1 } %pairval, 0
   ret i64 %val
 }
 
@@ -49,7 +53,8 @@ define i64 @f5(i64 %cmp, i64 %swap, i64 *%src) {
 ; CHECK: csg %r2, %r3, -524288(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i64 *%src, i64 -65536
-  %val = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %pairval = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %val = extractvalue { i64, i1 } %pairval, 0
   ret i64 %val
 }
 
@@ -61,7 +66,8 @@ define i64 @f6(i64 %cmp, i64 %swap, i64 *%src) {
 ; CHECK: csg %r2, %r3, 0(%r4)
 ; CHECK: br %r14
   %ptr = getelementptr i64 *%src, i64 -65537
-  %val = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %pairval = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %val = extractvalue { i64, i1 } %pairval, 0
   ret i64 %val
 }
 
@@ -73,7 +79,8 @@ define i64 @f7(i64 %cmp, i64 %swap, i64 %src, i64 %index) {
 ; CHECK: br %r14
   %add1 = add i64 %src, %index
   %ptr = inttoptr i64 %add1 to i64 *
-  %val = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %pairval = cmpxchg i64 *%ptr, i64 %cmp, i64 %swap seq_cst seq_cst
+  %val = extractvalue { i64, i1 } %pairval, 0
   ret i64 %val
 }
 
@@ -83,7 +90,8 @@ define i64 @f8(i64 %dummy, i64 %swap, i64 *%ptr) {
 ; CHECK: lghi %r2, 1001
 ; CHECK: csg %r2, %r3, 0(%r4)
 ; CHECK: br %r14
-  %val = cmpxchg i64 *%ptr, i64 1001, i64 %swap seq_cst seq_cst
+  %pairval = cmpxchg i64 *%ptr, i64 1001, i64 %swap seq_cst seq_cst
+  %val = extractvalue { i64, i1 } %pairval, 0
   ret i64 %val
 }
 
@@ -93,6 +101,7 @@ define i64 @f9(i64 %cmp, i64 *%ptr) {
 ; CHECK: lghi [[SWAP:%r[0-9]+]], 1002
 ; CHECK: csg %r2, [[SWAP]], 0(%r3)
 ; CHECK: br %r14
-  %val = cmpxchg i64 *%ptr, i64 %cmp, i64 1002 seq_cst seq_cst
+  %pairval = cmpxchg i64 *%ptr, i64 %cmp, i64 1002 seq_cst seq_cst
+  %val = extractvalue { i64, i1 } %pairval, 0
   ret i64 %val
 }