Support floating point values in 128-bit SSE vector registers

The System-V x86_64 ABI requires floating point values to be passed
in 128-but SSE vector registers (xmm0, ...). When printing such a
variable this currently yields an <invalid load address>.

This patch makes LLDB's DWARF expression evaluator accept 128-bit
registers as scalars. It also relaxes the check that the size of the
result of the DWARF expression be equal to the size of the variable to a
greater-than. DWARF defers to the ABI how smaller values are being placed
in a larger register.

Implementation note: I found the code in Value::SetContext() that changes
the m_value_type after the fact to be questionable. I added a sanity check
that the Value's memory buffer has indeed been written to (this is
necessary, because we may have a scalar value in a vector register), but
really I feel like this is the wrong place to be setting it.

Reviewed by Greg Clayton.

http://reviews.llvm.org/D17897
rdar://problem/24944340

llvm-svn: 262947

2 files changed, 27 insertions, 1 deletions

diff --git a/lldb/packages/Python/lldbsuite/test/lang/c/register_variables/TestRegisterVariables.py b/lldb/packages/Python/lldbsuite/test/lang/c/register_variables/TestRegisterVariables.py
index 0cb99238621..8fae3c982b0 100644
--- a/lldb/packages/Python/lldbsuite/test/lang/c/register_variables/TestRegisterVariables.py
+++ b/lldb/packages/Python/lldbsuite/test/lang/c/register_variables/TestRegisterVariables.py
@@ -24,7 +24,7 @@ class RegisterVariableTestCase(TestBase):
         self.runCmd("file " + exe, CURRENT_EXECUTABLE_SET)
 
         # Break inside the main.
-        lldbutil.run_break_set_by_source_regexp(self, "break", num_expected_locations=2)
+        lldbutil.run_break_set_by_source_regexp(self, "break", num_expected_locations=3)
 
         ####################
         # First breakpoint
@@ -68,4 +68,22 @@ class RegisterVariableTestCase(TestBase):
         self.expect("expr c", VARIABLES_DISPLAYED_CORRECTLY,
             substrs = ['(int) $3 = 5'])
 
+        #####################
+        # Third breakpoint
+
+        self.runCmd("continue")
+
+        # The stop reason of the thread should be breakpoint.
+        self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
+            substrs = ['stopped',
+                       'stop reason = breakpoint'])
+
+        # The breakpoint should have a hit count of 1.
+        self.expect("breakpoint list -f", BREAKPOINT_HIT_ONCE,
+            substrs = [' resolved, hit count = 1'])
+
+        # Try some variables that should be visible
+        self.expect("expr f", VARIABLES_DISPLAYED_CORRECTLY,
+            substrs = ['(float) $4 = 3.1'])
+
         self.runCmd("kill")
diff --git a/lldb/packages/Python/lldbsuite/test/lang/c/register_variables/test.c b/lldb/packages/Python/lldbsuite/test/lang/c/register_variables/test.c
index e467ac48f74..9acd3f3835b 100644
--- a/lldb/packages/Python/lldbsuite/test/lang/c/register_variables/test.c
+++ b/lldb/packages/Python/lldbsuite/test/lang/c/register_variables/test.c
@@ -18,10 +18,18 @@ void f2(struct bar *b)
   printf("%d\n", c); // set breakpoint here
 }
 
+float f3() __attribute__ ((noinline));
+float f3() {
+  return 3.14f;
+}
+
 int main()
 {
   struct bar myBar = { 3, 4 };
   f1(2, &myBar);
   f2(&myBar);
+
+  float f = f3();
+  printf("%f\n", f); // set breakpoint here
   return 0;
 }